Fri, 18 Feb 2011 10:07:34 -0800
7020042: G1: Partially remove fix for 6994628
Summary: Disable reference discovery and processing during concurrent marking by disabling fix for 6994628.
Reviewed-by: tonyp, ysr
1 /*
2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1MarkSweep.hpp"
35 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
36 #include "gc_implementation/g1/g1RemSet.inline.hpp"
37 #include "gc_implementation/g1/heapRegionRemSet.hpp"
38 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
39 #include "gc_implementation/g1/vm_operations_g1.hpp"
40 #include "gc_implementation/shared/isGCActiveMark.hpp"
41 #include "memory/gcLocker.inline.hpp"
42 #include "memory/genOopClosures.inline.hpp"
43 #include "memory/generationSpec.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "oops/oop.pcgc.inline.hpp"
46 #include "runtime/aprofiler.hpp"
47 #include "runtime/vmThread.hpp"
49 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
51 // turn it on so that the contents of the young list (scan-only /
52 // to-be-collected) are printed at "strategic" points before / during
53 // / after the collection --- this is useful for debugging
54 #define YOUNG_LIST_VERBOSE 0
55 // CURRENT STATUS
56 // This file is under construction. Search for "FIXME".
58 // INVARIANTS/NOTES
59 //
60 // All allocation activity covered by the G1CollectedHeap interface is
61 // serialized by acquiring the HeapLock. This happens in mem_allocate
62 // and allocate_new_tlab, which are the "entry" points to the
63 // allocation code from the rest of the JVM. (Note that this does not
64 // apply to TLAB allocation, which is not part of this interface: it
65 // is done by clients of this interface.)
67 // Local to this file.
69 class RefineCardTableEntryClosure: public CardTableEntryClosure {
70 SuspendibleThreadSet* _sts;
71 G1RemSet* _g1rs;
72 ConcurrentG1Refine* _cg1r;
73 bool _concurrent;
74 public:
75 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
76 G1RemSet* g1rs,
77 ConcurrentG1Refine* cg1r) :
78 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
79 {}
80 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
81 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
82 // This path is executed by the concurrent refine or mutator threads,
83 // concurrently, and so we do not care if card_ptr contains references
84 // that point into the collection set.
85 assert(!oops_into_cset, "should be");
87 if (_concurrent && _sts->should_yield()) {
88 // Caller will actually yield.
89 return false;
90 }
91 // Otherwise, we finished successfully; return true.
92 return true;
93 }
94 void set_concurrent(bool b) { _concurrent = b; }
95 };
98 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
99 int _calls;
100 G1CollectedHeap* _g1h;
101 CardTableModRefBS* _ctbs;
102 int _histo[256];
103 public:
104 ClearLoggedCardTableEntryClosure() :
105 _calls(0)
106 {
107 _g1h = G1CollectedHeap::heap();
108 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
109 for (int i = 0; i < 256; i++) _histo[i] = 0;
110 }
111 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
112 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
113 _calls++;
114 unsigned char* ujb = (unsigned char*)card_ptr;
115 int ind = (int)(*ujb);
116 _histo[ind]++;
117 *card_ptr = -1;
118 }
119 return true;
120 }
121 int calls() { return _calls; }
122 void print_histo() {
123 gclog_or_tty->print_cr("Card table value histogram:");
124 for (int i = 0; i < 256; i++) {
125 if (_histo[i] != 0) {
126 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
127 }
128 }
129 }
130 };
132 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
133 int _calls;
134 G1CollectedHeap* _g1h;
135 CardTableModRefBS* _ctbs;
136 public:
137 RedirtyLoggedCardTableEntryClosure() :
138 _calls(0)
139 {
140 _g1h = G1CollectedHeap::heap();
141 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
142 }
143 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
144 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
145 _calls++;
146 *card_ptr = 0;
147 }
148 return true;
149 }
150 int calls() { return _calls; }
151 };
153 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
154 public:
155 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
156 *card_ptr = CardTableModRefBS::dirty_card_val();
157 return true;
158 }
159 };
161 YoungList::YoungList(G1CollectedHeap* g1h)
162 : _g1h(g1h), _head(NULL),
163 _length(0),
164 _last_sampled_rs_lengths(0),
165 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0)
166 {
167 guarantee( check_list_empty(false), "just making sure..." );
168 }
170 void YoungList::push_region(HeapRegion *hr) {
171 assert(!hr->is_young(), "should not already be young");
172 assert(hr->get_next_young_region() == NULL, "cause it should!");
174 hr->set_next_young_region(_head);
175 _head = hr;
177 hr->set_young();
178 double yg_surv_rate = _g1h->g1_policy()->predict_yg_surv_rate((int)_length);
179 ++_length;
180 }
182 void YoungList::add_survivor_region(HeapRegion* hr) {
183 assert(hr->is_survivor(), "should be flagged as survivor region");
184 assert(hr->get_next_young_region() == NULL, "cause it should!");
186 hr->set_next_young_region(_survivor_head);
187 if (_survivor_head == NULL) {
188 _survivor_tail = hr;
189 }
190 _survivor_head = hr;
192 ++_survivor_length;
193 }
195 void YoungList::empty_list(HeapRegion* list) {
196 while (list != NULL) {
197 HeapRegion* next = list->get_next_young_region();
198 list->set_next_young_region(NULL);
199 list->uninstall_surv_rate_group();
200 list->set_not_young();
201 list = next;
202 }
203 }
205 void YoungList::empty_list() {
206 assert(check_list_well_formed(), "young list should be well formed");
208 empty_list(_head);
209 _head = NULL;
210 _length = 0;
212 empty_list(_survivor_head);
213 _survivor_head = NULL;
214 _survivor_tail = NULL;
215 _survivor_length = 0;
217 _last_sampled_rs_lengths = 0;
219 assert(check_list_empty(false), "just making sure...");
220 }
222 bool YoungList::check_list_well_formed() {
223 bool ret = true;
225 size_t length = 0;
226 HeapRegion* curr = _head;
227 HeapRegion* last = NULL;
228 while (curr != NULL) {
229 if (!curr->is_young()) {
230 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
231 "incorrectly tagged (y: %d, surv: %d)",
232 curr->bottom(), curr->end(),
233 curr->is_young(), curr->is_survivor());
234 ret = false;
235 }
236 ++length;
237 last = curr;
238 curr = curr->get_next_young_region();
239 }
240 ret = ret && (length == _length);
242 if (!ret) {
243 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
244 gclog_or_tty->print_cr("### list has %d entries, _length is %d",
245 length, _length);
246 }
248 return ret;
249 }
251 bool YoungList::check_list_empty(bool check_sample) {
252 bool ret = true;
254 if (_length != 0) {
255 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d",
256 _length);
257 ret = false;
258 }
259 if (check_sample && _last_sampled_rs_lengths != 0) {
260 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
261 ret = false;
262 }
263 if (_head != NULL) {
264 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
265 ret = false;
266 }
267 if (!ret) {
268 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
269 }
271 return ret;
272 }
274 void
275 YoungList::rs_length_sampling_init() {
276 _sampled_rs_lengths = 0;
277 _curr = _head;
278 }
280 bool
281 YoungList::rs_length_sampling_more() {
282 return _curr != NULL;
283 }
285 void
286 YoungList::rs_length_sampling_next() {
287 assert( _curr != NULL, "invariant" );
288 size_t rs_length = _curr->rem_set()->occupied();
290 _sampled_rs_lengths += rs_length;
292 // The current region may not yet have been added to the
293 // incremental collection set (it gets added when it is
294 // retired as the current allocation region).
295 if (_curr->in_collection_set()) {
296 // Update the collection set policy information for this region
297 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
298 }
300 _curr = _curr->get_next_young_region();
301 if (_curr == NULL) {
302 _last_sampled_rs_lengths = _sampled_rs_lengths;
303 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
304 }
305 }
307 void
308 YoungList::reset_auxilary_lists() {
309 guarantee( is_empty(), "young list should be empty" );
310 assert(check_list_well_formed(), "young list should be well formed");
312 // Add survivor regions to SurvRateGroup.
313 _g1h->g1_policy()->note_start_adding_survivor_regions();
314 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
316 for (HeapRegion* curr = _survivor_head;
317 curr != NULL;
318 curr = curr->get_next_young_region()) {
319 _g1h->g1_policy()->set_region_survivors(curr);
321 // The region is a non-empty survivor so let's add it to
322 // the incremental collection set for the next evacuation
323 // pause.
324 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
325 }
326 _g1h->g1_policy()->note_stop_adding_survivor_regions();
328 _head = _survivor_head;
329 _length = _survivor_length;
330 if (_survivor_head != NULL) {
331 assert(_survivor_tail != NULL, "cause it shouldn't be");
332 assert(_survivor_length > 0, "invariant");
333 _survivor_tail->set_next_young_region(NULL);
334 }
336 // Don't clear the survivor list handles until the start of
337 // the next evacuation pause - we need it in order to re-tag
338 // the survivor regions from this evacuation pause as 'young'
339 // at the start of the next.
341 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
343 assert(check_list_well_formed(), "young list should be well formed");
344 }
346 void YoungList::print() {
347 HeapRegion* lists[] = {_head, _survivor_head};
348 const char* names[] = {"YOUNG", "SURVIVOR"};
350 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
351 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
352 HeapRegion *curr = lists[list];
353 if (curr == NULL)
354 gclog_or_tty->print_cr(" empty");
355 while (curr != NULL) {
356 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
357 "age: %4d, y: %d, surv: %d",
358 curr->bottom(), curr->end(),
359 curr->top(),
360 curr->prev_top_at_mark_start(),
361 curr->next_top_at_mark_start(),
362 curr->top_at_conc_mark_count(),
363 curr->age_in_surv_rate_group_cond(),
364 curr->is_young(),
365 curr->is_survivor());
366 curr = curr->get_next_young_region();
367 }
368 }
370 gclog_or_tty->print_cr("");
371 }
373 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
374 {
375 // Claim the right to put the region on the dirty cards region list
376 // by installing a self pointer.
377 HeapRegion* next = hr->get_next_dirty_cards_region();
378 if (next == NULL) {
379 HeapRegion* res = (HeapRegion*)
380 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
381 NULL);
382 if (res == NULL) {
383 HeapRegion* head;
384 do {
385 // Put the region to the dirty cards region list.
386 head = _dirty_cards_region_list;
387 next = (HeapRegion*)
388 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
389 if (next == head) {
390 assert(hr->get_next_dirty_cards_region() == hr,
391 "hr->get_next_dirty_cards_region() != hr");
392 if (next == NULL) {
393 // The last region in the list points to itself.
394 hr->set_next_dirty_cards_region(hr);
395 } else {
396 hr->set_next_dirty_cards_region(next);
397 }
398 }
399 } while (next != head);
400 }
401 }
402 }
404 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
405 {
406 HeapRegion* head;
407 HeapRegion* hr;
408 do {
409 head = _dirty_cards_region_list;
410 if (head == NULL) {
411 return NULL;
412 }
413 HeapRegion* new_head = head->get_next_dirty_cards_region();
414 if (head == new_head) {
415 // The last region.
416 new_head = NULL;
417 }
418 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
419 head);
420 } while (hr != head);
421 assert(hr != NULL, "invariant");
422 hr->set_next_dirty_cards_region(NULL);
423 return hr;
424 }
426 void G1CollectedHeap::stop_conc_gc_threads() {
427 _cg1r->stop();
428 _cmThread->stop();
429 }
431 void G1CollectedHeap::check_ct_logs_at_safepoint() {
432 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
433 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
435 // Count the dirty cards at the start.
436 CountNonCleanMemRegionClosure count1(this);
437 ct_bs->mod_card_iterate(&count1);
438 int orig_count = count1.n();
440 // First clear the logged cards.
441 ClearLoggedCardTableEntryClosure clear;
442 dcqs.set_closure(&clear);
443 dcqs.apply_closure_to_all_completed_buffers();
444 dcqs.iterate_closure_all_threads(false);
445 clear.print_histo();
447 // Now ensure that there's no dirty cards.
448 CountNonCleanMemRegionClosure count2(this);
449 ct_bs->mod_card_iterate(&count2);
450 if (count2.n() != 0) {
451 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
452 count2.n(), orig_count);
453 }
454 guarantee(count2.n() == 0, "Card table should be clean.");
456 RedirtyLoggedCardTableEntryClosure redirty;
457 JavaThread::dirty_card_queue_set().set_closure(&redirty);
458 dcqs.apply_closure_to_all_completed_buffers();
459 dcqs.iterate_closure_all_threads(false);
460 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
461 clear.calls(), orig_count);
462 guarantee(redirty.calls() == clear.calls(),
463 "Or else mechanism is broken.");
465 CountNonCleanMemRegionClosure count3(this);
466 ct_bs->mod_card_iterate(&count3);
467 if (count3.n() != orig_count) {
468 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
469 orig_count, count3.n());
470 guarantee(count3.n() >= orig_count, "Should have restored them all.");
471 }
473 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
474 }
476 // Private class members.
478 G1CollectedHeap* G1CollectedHeap::_g1h;
480 // Private methods.
482 HeapRegion*
483 G1CollectedHeap::new_region_try_secondary_free_list() {
484 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
485 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
486 if (!_secondary_free_list.is_empty()) {
487 if (G1ConcRegionFreeingVerbose) {
488 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
489 "secondary_free_list has "SIZE_FORMAT" entries",
490 _secondary_free_list.length());
491 }
492 // It looks as if there are free regions available on the
493 // secondary_free_list. Let's move them to the free_list and try
494 // again to allocate from it.
495 append_secondary_free_list();
497 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
498 "empty we should have moved at least one entry to the free_list");
499 HeapRegion* res = _free_list.remove_head();
500 if (G1ConcRegionFreeingVerbose) {
501 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
502 "allocated "HR_FORMAT" from secondary_free_list",
503 HR_FORMAT_PARAMS(res));
504 }
505 return res;
506 }
508 // Wait here until we get notifed either when (a) there are no
509 // more free regions coming or (b) some regions have been moved on
510 // the secondary_free_list.
511 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
512 }
514 if (G1ConcRegionFreeingVerbose) {
515 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
516 "could not allocate from secondary_free_list");
517 }
518 return NULL;
519 }
521 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
522 assert(!isHumongous(word_size) ||
523 word_size <= (size_t) HeapRegion::GrainWords,
524 "the only time we use this to allocate a humongous region is "
525 "when we are allocating a single humongous region");
527 HeapRegion* res;
528 if (G1StressConcRegionFreeing) {
529 if (!_secondary_free_list.is_empty()) {
530 if (G1ConcRegionFreeingVerbose) {
531 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
532 "forced to look at the secondary_free_list");
533 }
534 res = new_region_try_secondary_free_list();
535 if (res != NULL) {
536 return res;
537 }
538 }
539 }
540 res = _free_list.remove_head_or_null();
541 if (res == NULL) {
542 if (G1ConcRegionFreeingVerbose) {
543 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
544 "res == NULL, trying the secondary_free_list");
545 }
546 res = new_region_try_secondary_free_list();
547 }
548 if (res == NULL && do_expand) {
549 if (expand(word_size * HeapWordSize)) {
550 // The expansion succeeded and so we should have at least one
551 // region on the free list.
552 res = _free_list.remove_head();
553 }
554 }
555 if (res != NULL) {
556 if (G1PrintHeapRegions) {
557 gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT","PTR_FORMAT"], "
558 "top "PTR_FORMAT, res->hrs_index(),
559 res->bottom(), res->end(), res->top());
560 }
561 }
562 return res;
563 }
565 HeapRegion* G1CollectedHeap::new_gc_alloc_region(int purpose,
566 size_t word_size) {
567 HeapRegion* alloc_region = NULL;
568 if (_gc_alloc_region_counts[purpose] < g1_policy()->max_regions(purpose)) {
569 alloc_region = new_region(word_size, true /* do_expand */);
570 if (purpose == GCAllocForSurvived && alloc_region != NULL) {
571 alloc_region->set_survivor();
572 }
573 ++_gc_alloc_region_counts[purpose];
574 } else {
575 g1_policy()->note_alloc_region_limit_reached(purpose);
576 }
577 return alloc_region;
578 }
580 int G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
581 size_t word_size) {
582 assert(isHumongous(word_size), "word_size should be humongous");
583 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
585 int first = -1;
586 if (num_regions == 1) {
587 // Only one region to allocate, no need to go through the slower
588 // path. The caller will attempt the expasion if this fails, so
589 // let's not try to expand here too.
590 HeapRegion* hr = new_region(word_size, false /* do_expand */);
591 if (hr != NULL) {
592 first = hr->hrs_index();
593 } else {
594 first = -1;
595 }
596 } else {
597 // We can't allocate humongous regions while cleanupComplete() is
598 // running, since some of the regions we find to be empty might not
599 // yet be added to the free list and it is not straightforward to
600 // know which list they are on so that we can remove them. Note
601 // that we only need to do this if we need to allocate more than
602 // one region to satisfy the current humongous allocation
603 // request. If we are only allocating one region we use the common
604 // region allocation code (see above).
605 wait_while_free_regions_coming();
606 append_secondary_free_list_if_not_empty_with_lock();
608 if (free_regions() >= num_regions) {
609 first = _hrs->find_contiguous(num_regions);
610 if (first != -1) {
611 for (int i = first; i < first + (int) num_regions; ++i) {
612 HeapRegion* hr = _hrs->at(i);
613 assert(hr->is_empty(), "sanity");
614 assert(is_on_master_free_list(hr), "sanity");
615 hr->set_pending_removal(true);
616 }
617 _free_list.remove_all_pending(num_regions);
618 }
619 }
620 }
621 return first;
622 }
624 HeapWord*
625 G1CollectedHeap::humongous_obj_allocate_initialize_regions(int first,
626 size_t num_regions,
627 size_t word_size) {
628 assert(first != -1, "pre-condition");
629 assert(isHumongous(word_size), "word_size should be humongous");
630 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
632 // Index of last region in the series + 1.
633 int last = first + (int) num_regions;
635 // We need to initialize the region(s) we just discovered. This is
636 // a bit tricky given that it can happen concurrently with
637 // refinement threads refining cards on these regions and
638 // potentially wanting to refine the BOT as they are scanning
639 // those cards (this can happen shortly after a cleanup; see CR
640 // 6991377). So we have to set up the region(s) carefully and in
641 // a specific order.
643 // The word size sum of all the regions we will allocate.
644 size_t word_size_sum = num_regions * HeapRegion::GrainWords;
645 assert(word_size <= word_size_sum, "sanity");
647 // This will be the "starts humongous" region.
648 HeapRegion* first_hr = _hrs->at(first);
649 // The header of the new object will be placed at the bottom of
650 // the first region.
651 HeapWord* new_obj = first_hr->bottom();
652 // This will be the new end of the first region in the series that
653 // should also match the end of the last region in the seriers.
654 HeapWord* new_end = new_obj + word_size_sum;
655 // This will be the new top of the first region that will reflect
656 // this allocation.
657 HeapWord* new_top = new_obj + word_size;
659 // First, we need to zero the header of the space that we will be
660 // allocating. When we update top further down, some refinement
661 // threads might try to scan the region. By zeroing the header we
662 // ensure that any thread that will try to scan the region will
663 // come across the zero klass word and bail out.
664 //
665 // NOTE: It would not have been correct to have used
666 // CollectedHeap::fill_with_object() and make the space look like
667 // an int array. The thread that is doing the allocation will
668 // later update the object header to a potentially different array
669 // type and, for a very short period of time, the klass and length
670 // fields will be inconsistent. This could cause a refinement
671 // thread to calculate the object size incorrectly.
672 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
674 // We will set up the first region as "starts humongous". This
675 // will also update the BOT covering all the regions to reflect
676 // that there is a single object that starts at the bottom of the
677 // first region.
678 first_hr->set_startsHumongous(new_top, new_end);
680 // Then, if there are any, we will set up the "continues
681 // humongous" regions.
682 HeapRegion* hr = NULL;
683 for (int i = first + 1; i < last; ++i) {
684 hr = _hrs->at(i);
685 hr->set_continuesHumongous(first_hr);
686 }
687 // If we have "continues humongous" regions (hr != NULL), then the
688 // end of the last one should match new_end.
689 assert(hr == NULL || hr->end() == new_end, "sanity");
691 // Up to this point no concurrent thread would have been able to
692 // do any scanning on any region in this series. All the top
693 // fields still point to bottom, so the intersection between
694 // [bottom,top] and [card_start,card_end] will be empty. Before we
695 // update the top fields, we'll do a storestore to make sure that
696 // no thread sees the update to top before the zeroing of the
697 // object header and the BOT initialization.
698 OrderAccess::storestore();
700 // Now that the BOT and the object header have been initialized,
701 // we can update top of the "starts humongous" region.
702 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
703 "new_top should be in this region");
704 first_hr->set_top(new_top);
706 // Now, we will update the top fields of the "continues humongous"
707 // regions. The reason we need to do this is that, otherwise,
708 // these regions would look empty and this will confuse parts of
709 // G1. For example, the code that looks for a consecutive number
710 // of empty regions will consider them empty and try to
711 // re-allocate them. We can extend is_empty() to also include
712 // !continuesHumongous(), but it is easier to just update the top
713 // fields here. The way we set top for all regions (i.e., top ==
714 // end for all regions but the last one, top == new_top for the
715 // last one) is actually used when we will free up the humongous
716 // region in free_humongous_region().
717 hr = NULL;
718 for (int i = first + 1; i < last; ++i) {
719 hr = _hrs->at(i);
720 if ((i + 1) == last) {
721 // last continues humongous region
722 assert(hr->bottom() < new_top && new_top <= hr->end(),
723 "new_top should fall on this region");
724 hr->set_top(new_top);
725 } else {
726 // not last one
727 assert(new_top > hr->end(), "new_top should be above this region");
728 hr->set_top(hr->end());
729 }
730 }
731 // If we have continues humongous regions (hr != NULL), then the
732 // end of the last one should match new_end and its top should
733 // match new_top.
734 assert(hr == NULL ||
735 (hr->end() == new_end && hr->top() == new_top), "sanity");
737 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
738 _summary_bytes_used += first_hr->used();
739 _humongous_set.add(first_hr);
741 return new_obj;
742 }
744 // If could fit into free regions w/o expansion, try.
745 // Otherwise, if can expand, do so.
746 // Otherwise, if using ex regions might help, try with ex given back.
747 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
748 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
750 verify_region_sets_optional();
752 size_t num_regions =
753 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
754 size_t x_size = expansion_regions();
755 size_t fs = _hrs->free_suffix();
756 int first = humongous_obj_allocate_find_first(num_regions, word_size);
757 if (first == -1) {
758 // The only thing we can do now is attempt expansion.
759 if (fs + x_size >= num_regions) {
760 // If the number of regions we're trying to allocate for this
761 // object is at most the number of regions in the free suffix,
762 // then the call to humongous_obj_allocate_find_first() above
763 // should have succeeded and we wouldn't be here.
764 //
765 // We should only be trying to expand when the free suffix is
766 // not sufficient for the object _and_ we have some expansion
767 // room available.
768 assert(num_regions > fs, "earlier allocation should have succeeded");
770 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
771 first = humongous_obj_allocate_find_first(num_regions, word_size);
772 // If the expansion was successful then the allocation
773 // should have been successful.
774 assert(first != -1, "this should have worked");
775 }
776 }
777 }
779 HeapWord* result = NULL;
780 if (first != -1) {
781 result =
782 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
783 assert(result != NULL, "it should always return a valid result");
784 }
786 verify_region_sets_optional();
788 return result;
789 }
791 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
792 assert_heap_not_locked_and_not_at_safepoint();
793 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
795 unsigned int dummy_gc_count_before;
796 return attempt_allocation(word_size, &dummy_gc_count_before);
797 }
799 HeapWord*
800 G1CollectedHeap::mem_allocate(size_t word_size,
801 bool is_noref,
802 bool is_tlab,
803 bool* gc_overhead_limit_was_exceeded) {
804 assert_heap_not_locked_and_not_at_safepoint();
805 assert(!is_tlab, "mem_allocate() this should not be called directly "
806 "to allocate TLABs");
808 // Loop until the allocation is satisified, or unsatisfied after GC.
809 for (int try_count = 1; /* we'll return */; try_count += 1) {
810 unsigned int gc_count_before;
812 HeapWord* result = NULL;
813 if (!isHumongous(word_size)) {
814 result = attempt_allocation(word_size, &gc_count_before);
815 } else {
816 result = attempt_allocation_humongous(word_size, &gc_count_before);
817 }
818 if (result != NULL) {
819 return result;
820 }
822 // Create the garbage collection operation...
823 VM_G1CollectForAllocation op(gc_count_before, word_size);
824 // ...and get the VM thread to execute it.
825 VMThread::execute(&op);
827 if (op.prologue_succeeded() && op.pause_succeeded()) {
828 // If the operation was successful we'll return the result even
829 // if it is NULL. If the allocation attempt failed immediately
830 // after a Full GC, it's unlikely we'll be able to allocate now.
831 HeapWord* result = op.result();
832 if (result != NULL && !isHumongous(word_size)) {
833 // Allocations that take place on VM operations do not do any
834 // card dirtying and we have to do it here. We only have to do
835 // this for non-humongous allocations, though.
836 dirty_young_block(result, word_size);
837 }
838 return result;
839 } else {
840 assert(op.result() == NULL,
841 "the result should be NULL if the VM op did not succeed");
842 }
844 // Give a warning if we seem to be looping forever.
845 if ((QueuedAllocationWarningCount > 0) &&
846 (try_count % QueuedAllocationWarningCount == 0)) {
847 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
848 }
849 }
851 ShouldNotReachHere();
852 return NULL;
853 }
855 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
856 unsigned int *gc_count_before_ret) {
857 // Make sure you read the note in attempt_allocation_humongous().
859 assert_heap_not_locked_and_not_at_safepoint();
860 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
861 "be called for humongous allocation requests");
863 // We should only get here after the first-level allocation attempt
864 // (attempt_allocation()) failed to allocate.
866 // We will loop until a) we manage to successfully perform the
867 // allocation or b) we successfully schedule a collection which
868 // fails to perform the allocation. b) is the only case when we'll
869 // return NULL.
870 HeapWord* result = NULL;
871 for (int try_count = 1; /* we'll return */; try_count += 1) {
872 bool should_try_gc;
873 unsigned int gc_count_before;
875 {
876 MutexLockerEx x(Heap_lock);
878 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
879 false /* bot_updates */);
880 if (result != NULL) {
881 return result;
882 }
884 // If we reach here, attempt_allocation_locked() above failed to
885 // allocate a new region. So the mutator alloc region should be NULL.
886 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
888 if (GC_locker::is_active_and_needs_gc()) {
889 if (g1_policy()->can_expand_young_list()) {
890 result = _mutator_alloc_region.attempt_allocation_force(word_size,
891 false /* bot_updates */);
892 if (result != NULL) {
893 return result;
894 }
895 }
896 should_try_gc = false;
897 } else {
898 // Read the GC count while still holding the Heap_lock.
899 gc_count_before = SharedHeap::heap()->total_collections();
900 should_try_gc = true;
901 }
902 }
904 if (should_try_gc) {
905 bool succeeded;
906 result = do_collection_pause(word_size, gc_count_before, &succeeded);
907 if (result != NULL) {
908 assert(succeeded, "only way to get back a non-NULL result");
909 return result;
910 }
912 if (succeeded) {
913 // If we get here we successfully scheduled a collection which
914 // failed to allocate. No point in trying to allocate
915 // further. We'll just return NULL.
916 MutexLockerEx x(Heap_lock);
917 *gc_count_before_ret = SharedHeap::heap()->total_collections();
918 return NULL;
919 }
920 } else {
921 GC_locker::stall_until_clear();
922 }
924 // We can reach here if we were unsuccessul in scheduling a
925 // collection (because another thread beat us to it) or if we were
926 // stalled due to the GC locker. In either can we should retry the
927 // allocation attempt in case another thread successfully
928 // performed a collection and reclaimed enough space. We do the
929 // first attempt (without holding the Heap_lock) here and the
930 // follow-on attempt will be at the start of the next loop
931 // iteration (after taking the Heap_lock).
932 result = _mutator_alloc_region.attempt_allocation(word_size,
933 false /* bot_updates */);
934 if (result != NULL ){
935 return result;
936 }
938 // Give a warning if we seem to be looping forever.
939 if ((QueuedAllocationWarningCount > 0) &&
940 (try_count % QueuedAllocationWarningCount == 0)) {
941 warning("G1CollectedHeap::attempt_allocation_slow() "
942 "retries %d times", try_count);
943 }
944 }
946 ShouldNotReachHere();
947 return NULL;
948 }
950 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
951 unsigned int * gc_count_before_ret) {
952 // The structure of this method has a lot of similarities to
953 // attempt_allocation_slow(). The reason these two were not merged
954 // into a single one is that such a method would require several "if
955 // allocation is not humongous do this, otherwise do that"
956 // conditional paths which would obscure its flow. In fact, an early
957 // version of this code did use a unified method which was harder to
958 // follow and, as a result, it had subtle bugs that were hard to
959 // track down. So keeping these two methods separate allows each to
960 // be more readable. It will be good to keep these two in sync as
961 // much as possible.
963 assert_heap_not_locked_and_not_at_safepoint();
964 assert(isHumongous(word_size), "attempt_allocation_humongous() "
965 "should only be called for humongous allocations");
967 // We will loop until a) we manage to successfully perform the
968 // allocation or b) we successfully schedule a collection which
969 // fails to perform the allocation. b) is the only case when we'll
970 // return NULL.
971 HeapWord* result = NULL;
972 for (int try_count = 1; /* we'll return */; try_count += 1) {
973 bool should_try_gc;
974 unsigned int gc_count_before;
976 {
977 MutexLockerEx x(Heap_lock);
979 // Given that humongous objects are not allocated in young
980 // regions, we'll first try to do the allocation without doing a
981 // collection hoping that there's enough space in the heap.
982 result = humongous_obj_allocate(word_size);
983 if (result != NULL) {
984 return result;
985 }
987 if (GC_locker::is_active_and_needs_gc()) {
988 should_try_gc = false;
989 } else {
990 // Read the GC count while still holding the Heap_lock.
991 gc_count_before = SharedHeap::heap()->total_collections();
992 should_try_gc = true;
993 }
994 }
996 if (should_try_gc) {
997 // If we failed to allocate the humongous object, we should try to
998 // do a collection pause (if we're allowed) in case it reclaims
999 // enough space for the allocation to succeed after the pause.
1001 bool succeeded;
1002 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1003 if (result != NULL) {
1004 assert(succeeded, "only way to get back a non-NULL result");
1005 return result;
1006 }
1008 if (succeeded) {
1009 // If we get here we successfully scheduled a collection which
1010 // failed to allocate. No point in trying to allocate
1011 // further. We'll just return NULL.
1012 MutexLockerEx x(Heap_lock);
1013 *gc_count_before_ret = SharedHeap::heap()->total_collections();
1014 return NULL;
1015 }
1016 } else {
1017 GC_locker::stall_until_clear();
1018 }
1020 // We can reach here if we were unsuccessul in scheduling a
1021 // collection (because another thread beat us to it) or if we were
1022 // stalled due to the GC locker. In either can we should retry the
1023 // allocation attempt in case another thread successfully
1024 // performed a collection and reclaimed enough space. Give a
1025 // warning if we seem to be looping forever.
1027 if ((QueuedAllocationWarningCount > 0) &&
1028 (try_count % QueuedAllocationWarningCount == 0)) {
1029 warning("G1CollectedHeap::attempt_allocation_humongous() "
1030 "retries %d times", try_count);
1031 }
1032 }
1034 ShouldNotReachHere();
1035 return NULL;
1036 }
1038 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1039 bool expect_null_mutator_alloc_region) {
1040 assert_at_safepoint(true /* should_be_vm_thread */);
1041 assert(_mutator_alloc_region.get() == NULL ||
1042 !expect_null_mutator_alloc_region,
1043 "the current alloc region was unexpectedly found to be non-NULL");
1045 if (!isHumongous(word_size)) {
1046 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1047 false /* bot_updates */);
1048 } else {
1049 return humongous_obj_allocate(word_size);
1050 }
1052 ShouldNotReachHere();
1053 }
1055 void G1CollectedHeap::abandon_gc_alloc_regions() {
1056 // first, make sure that the GC alloc region list is empty (it should!)
1057 assert(_gc_alloc_region_list == NULL, "invariant");
1058 release_gc_alloc_regions(true /* totally */);
1059 }
1061 class PostMCRemSetClearClosure: public HeapRegionClosure {
1062 ModRefBarrierSet* _mr_bs;
1063 public:
1064 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1065 bool doHeapRegion(HeapRegion* r) {
1066 r->reset_gc_time_stamp();
1067 if (r->continuesHumongous())
1068 return false;
1069 HeapRegionRemSet* hrrs = r->rem_set();
1070 if (hrrs != NULL) hrrs->clear();
1071 // You might think here that we could clear just the cards
1072 // corresponding to the used region. But no: if we leave a dirty card
1073 // in a region we might allocate into, then it would prevent that card
1074 // from being enqueued, and cause it to be missed.
1075 // Re: the performance cost: we shouldn't be doing full GC anyway!
1076 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1077 return false;
1078 }
1079 };
1082 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1083 ModRefBarrierSet* _mr_bs;
1084 public:
1085 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1086 bool doHeapRegion(HeapRegion* r) {
1087 if (r->continuesHumongous()) return false;
1088 if (r->used_region().word_size() != 0) {
1089 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1090 }
1091 return false;
1092 }
1093 };
1095 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1096 G1CollectedHeap* _g1h;
1097 UpdateRSOopClosure _cl;
1098 int _worker_i;
1099 public:
1100 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1101 _cl(g1->g1_rem_set(), worker_i),
1102 _worker_i(worker_i),
1103 _g1h(g1)
1104 { }
1106 bool doHeapRegion(HeapRegion* r) {
1107 if (!r->continuesHumongous()) {
1108 _cl.set_from(r);
1109 r->oop_iterate(&_cl);
1110 }
1111 return false;
1112 }
1113 };
1115 class ParRebuildRSTask: public AbstractGangTask {
1116 G1CollectedHeap* _g1;
1117 public:
1118 ParRebuildRSTask(G1CollectedHeap* g1)
1119 : AbstractGangTask("ParRebuildRSTask"),
1120 _g1(g1)
1121 { }
1123 void work(int i) {
1124 RebuildRSOutOfRegionClosure rebuild_rs(_g1, i);
1125 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
1126 HeapRegion::RebuildRSClaimValue);
1127 }
1128 };
1130 bool G1CollectedHeap::do_collection(bool explicit_gc,
1131 bool clear_all_soft_refs,
1132 size_t word_size) {
1133 assert_at_safepoint(true /* should_be_vm_thread */);
1135 if (GC_locker::check_active_before_gc()) {
1136 return false;
1137 }
1139 SvcGCMarker sgcm(SvcGCMarker::FULL);
1140 ResourceMark rm;
1142 if (PrintHeapAtGC) {
1143 Universe::print_heap_before_gc();
1144 }
1146 verify_region_sets_optional();
1148 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1149 collector_policy()->should_clear_all_soft_refs();
1151 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1153 {
1154 IsGCActiveMark x;
1156 // Timing
1157 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1158 assert(!system_gc || explicit_gc, "invariant");
1159 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
1160 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
1161 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1162 PrintGC, true, gclog_or_tty);
1164 TraceMemoryManagerStats tms(true /* fullGC */);
1166 double start = os::elapsedTime();
1167 g1_policy()->record_full_collection_start();
1169 wait_while_free_regions_coming();
1170 append_secondary_free_list_if_not_empty_with_lock();
1172 gc_prologue(true);
1173 increment_total_collections(true /* full gc */);
1175 size_t g1h_prev_used = used();
1176 assert(used() == recalculate_used(), "Should be equal");
1178 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1179 HandleMark hm; // Discard invalid handles created during verification
1180 gclog_or_tty->print(" VerifyBeforeGC:");
1181 prepare_for_verify();
1182 Universe::verify(true);
1183 }
1185 COMPILER2_PRESENT(DerivedPointerTable::clear());
1187 // We want to discover references, but not process them yet.
1188 // This mode is disabled in
1189 // instanceRefKlass::process_discovered_references if the
1190 // generation does some collection work, or
1191 // instanceRefKlass::enqueue_discovered_references if the
1192 // generation returns without doing any work.
1193 ref_processor()->disable_discovery();
1194 ref_processor()->abandon_partial_discovery();
1195 ref_processor()->verify_no_references_recorded();
1197 // Abandon current iterations of concurrent marking and concurrent
1198 // refinement, if any are in progress.
1199 concurrent_mark()->abort();
1201 // Make sure we'll choose a new allocation region afterwards.
1202 release_mutator_alloc_region();
1203 abandon_gc_alloc_regions();
1204 g1_rem_set()->cleanupHRRS();
1205 tear_down_region_lists();
1207 // We may have added regions to the current incremental collection
1208 // set between the last GC or pause and now. We need to clear the
1209 // incremental collection set and then start rebuilding it afresh
1210 // after this full GC.
1211 abandon_collection_set(g1_policy()->inc_cset_head());
1212 g1_policy()->clear_incremental_cset();
1213 g1_policy()->stop_incremental_cset_building();
1215 if (g1_policy()->in_young_gc_mode()) {
1216 empty_young_list();
1217 g1_policy()->set_full_young_gcs(true);
1218 }
1220 // See the comment in G1CollectedHeap::ref_processing_init() about
1221 // how reference processing currently works in G1.
1223 // Temporarily make reference _discovery_ single threaded (non-MT).
1224 ReferenceProcessorMTDiscoveryMutator rp_disc_ser(ref_processor(), false);
1226 // Temporarily make refs discovery atomic
1227 ReferenceProcessorAtomicMutator rp_disc_atomic(ref_processor(), true);
1229 // Temporarily clear _is_alive_non_header
1230 ReferenceProcessorIsAliveMutator rp_is_alive_null(ref_processor(), NULL);
1232 ref_processor()->enable_discovery();
1233 ref_processor()->setup_policy(do_clear_all_soft_refs);
1235 // Do collection work
1236 {
1237 HandleMark hm; // Discard invalid handles created during gc
1238 G1MarkSweep::invoke_at_safepoint(ref_processor(), do_clear_all_soft_refs);
1239 }
1240 assert(free_regions() == 0, "we should not have added any free regions");
1241 rebuild_region_lists();
1243 _summary_bytes_used = recalculate_used();
1245 ref_processor()->enqueue_discovered_references();
1247 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1249 MemoryService::track_memory_usage();
1251 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1252 HandleMark hm; // Discard invalid handles created during verification
1253 gclog_or_tty->print(" VerifyAfterGC:");
1254 prepare_for_verify();
1255 Universe::verify(false);
1256 }
1257 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1259 reset_gc_time_stamp();
1260 // Since everything potentially moved, we will clear all remembered
1261 // sets, and clear all cards. Later we will rebuild remebered
1262 // sets. We will also reset the GC time stamps of the regions.
1263 PostMCRemSetClearClosure rs_clear(mr_bs());
1264 heap_region_iterate(&rs_clear);
1266 // Resize the heap if necessary.
1267 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1269 if (_cg1r->use_cache()) {
1270 _cg1r->clear_and_record_card_counts();
1271 _cg1r->clear_hot_cache();
1272 }
1274 // Rebuild remembered sets of all regions.
1276 if (G1CollectedHeap::use_parallel_gc_threads()) {
1277 ParRebuildRSTask rebuild_rs_task(this);
1278 assert(check_heap_region_claim_values(
1279 HeapRegion::InitialClaimValue), "sanity check");
1280 set_par_threads(workers()->total_workers());
1281 workers()->run_task(&rebuild_rs_task);
1282 set_par_threads(0);
1283 assert(check_heap_region_claim_values(
1284 HeapRegion::RebuildRSClaimValue), "sanity check");
1285 reset_heap_region_claim_values();
1286 } else {
1287 RebuildRSOutOfRegionClosure rebuild_rs(this);
1288 heap_region_iterate(&rebuild_rs);
1289 }
1291 if (PrintGC) {
1292 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1293 }
1295 if (true) { // FIXME
1296 // Ask the permanent generation to adjust size for full collections
1297 perm()->compute_new_size();
1298 }
1300 // Start a new incremental collection set for the next pause
1301 assert(g1_policy()->collection_set() == NULL, "must be");
1302 g1_policy()->start_incremental_cset_building();
1304 // Clear the _cset_fast_test bitmap in anticipation of adding
1305 // regions to the incremental collection set for the next
1306 // evacuation pause.
1307 clear_cset_fast_test();
1309 init_mutator_alloc_region();
1311 double end = os::elapsedTime();
1312 g1_policy()->record_full_collection_end();
1314 #ifdef TRACESPINNING
1315 ParallelTaskTerminator::print_termination_counts();
1316 #endif
1318 gc_epilogue(true);
1320 // Discard all rset updates
1321 JavaThread::dirty_card_queue_set().abandon_logs();
1322 assert(!G1DeferredRSUpdate
1323 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1324 }
1326 if (g1_policy()->in_young_gc_mode()) {
1327 _young_list->reset_sampled_info();
1328 // At this point there should be no regions in the
1329 // entire heap tagged as young.
1330 assert( check_young_list_empty(true /* check_heap */),
1331 "young list should be empty at this point");
1332 }
1334 // Update the number of full collections that have been completed.
1335 increment_full_collections_completed(false /* concurrent */);
1337 verify_region_sets_optional();
1339 if (PrintHeapAtGC) {
1340 Universe::print_heap_after_gc();
1341 }
1343 return true;
1344 }
1346 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1347 // do_collection() will return whether it succeeded in performing
1348 // the GC. Currently, there is no facility on the
1349 // do_full_collection() API to notify the caller than the collection
1350 // did not succeed (e.g., because it was locked out by the GC
1351 // locker). So, right now, we'll ignore the return value.
1352 bool dummy = do_collection(true, /* explicit_gc */
1353 clear_all_soft_refs,
1354 0 /* word_size */);
1355 }
1357 // This code is mostly copied from TenuredGeneration.
1358 void
1359 G1CollectedHeap::
1360 resize_if_necessary_after_full_collection(size_t word_size) {
1361 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1363 // Include the current allocation, if any, and bytes that will be
1364 // pre-allocated to support collections, as "used".
1365 const size_t used_after_gc = used();
1366 const size_t capacity_after_gc = capacity();
1367 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1369 // This is enforced in arguments.cpp.
1370 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1371 "otherwise the code below doesn't make sense");
1373 // We don't have floating point command-line arguments
1374 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1375 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1376 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1377 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1379 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1380 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1382 // We have to be careful here as these two calculations can overflow
1383 // 32-bit size_t's.
1384 double used_after_gc_d = (double) used_after_gc;
1385 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1386 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1388 // Let's make sure that they are both under the max heap size, which
1389 // by default will make them fit into a size_t.
1390 double desired_capacity_upper_bound = (double) max_heap_size;
1391 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1392 desired_capacity_upper_bound);
1393 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1394 desired_capacity_upper_bound);
1396 // We can now safely turn them into size_t's.
1397 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1398 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1400 // This assert only makes sense here, before we adjust them
1401 // with respect to the min and max heap size.
1402 assert(minimum_desired_capacity <= maximum_desired_capacity,
1403 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1404 "maximum_desired_capacity = "SIZE_FORMAT,
1405 minimum_desired_capacity, maximum_desired_capacity));
1407 // Should not be greater than the heap max size. No need to adjust
1408 // it with respect to the heap min size as it's a lower bound (i.e.,
1409 // we'll try to make the capacity larger than it, not smaller).
1410 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1411 // Should not be less than the heap min size. No need to adjust it
1412 // with respect to the heap max size as it's an upper bound (i.e.,
1413 // we'll try to make the capacity smaller than it, not greater).
1414 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1416 if (PrintGC && Verbose) {
1417 const double free_percentage =
1418 (double) free_after_gc / (double) capacity_after_gc;
1419 gclog_or_tty->print_cr("Computing new size after full GC ");
1420 gclog_or_tty->print_cr(" "
1421 " minimum_free_percentage: %6.2f",
1422 minimum_free_percentage);
1423 gclog_or_tty->print_cr(" "
1424 " maximum_free_percentage: %6.2f",
1425 maximum_free_percentage);
1426 gclog_or_tty->print_cr(" "
1427 " capacity: %6.1fK"
1428 " minimum_desired_capacity: %6.1fK"
1429 " maximum_desired_capacity: %6.1fK",
1430 (double) capacity_after_gc / (double) K,
1431 (double) minimum_desired_capacity / (double) K,
1432 (double) maximum_desired_capacity / (double) K);
1433 gclog_or_tty->print_cr(" "
1434 " free_after_gc: %6.1fK"
1435 " used_after_gc: %6.1fK",
1436 (double) free_after_gc / (double) K,
1437 (double) used_after_gc / (double) K);
1438 gclog_or_tty->print_cr(" "
1439 " free_percentage: %6.2f",
1440 free_percentage);
1441 }
1442 if (capacity_after_gc < minimum_desired_capacity) {
1443 // Don't expand unless it's significant
1444 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1445 if (expand(expand_bytes)) {
1446 if (PrintGC && Verbose) {
1447 gclog_or_tty->print_cr(" "
1448 " expanding:"
1449 " max_heap_size: %6.1fK"
1450 " minimum_desired_capacity: %6.1fK"
1451 " expand_bytes: %6.1fK",
1452 (double) max_heap_size / (double) K,
1453 (double) minimum_desired_capacity / (double) K,
1454 (double) expand_bytes / (double) K);
1455 }
1456 }
1458 // No expansion, now see if we want to shrink
1459 } else if (capacity_after_gc > maximum_desired_capacity) {
1460 // Capacity too large, compute shrinking size
1461 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1462 shrink(shrink_bytes);
1463 if (PrintGC && Verbose) {
1464 gclog_or_tty->print_cr(" "
1465 " shrinking:"
1466 " min_heap_size: %6.1fK"
1467 " maximum_desired_capacity: %6.1fK"
1468 " shrink_bytes: %6.1fK",
1469 (double) min_heap_size / (double) K,
1470 (double) maximum_desired_capacity / (double) K,
1471 (double) shrink_bytes / (double) K);
1472 }
1473 }
1474 }
1477 HeapWord*
1478 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1479 bool* succeeded) {
1480 assert_at_safepoint(true /* should_be_vm_thread */);
1482 *succeeded = true;
1483 // Let's attempt the allocation first.
1484 HeapWord* result =
1485 attempt_allocation_at_safepoint(word_size,
1486 false /* expect_null_mutator_alloc_region */);
1487 if (result != NULL) {
1488 assert(*succeeded, "sanity");
1489 return result;
1490 }
1492 // In a G1 heap, we're supposed to keep allocation from failing by
1493 // incremental pauses. Therefore, at least for now, we'll favor
1494 // expansion over collection. (This might change in the future if we can
1495 // do something smarter than full collection to satisfy a failed alloc.)
1496 result = expand_and_allocate(word_size);
1497 if (result != NULL) {
1498 assert(*succeeded, "sanity");
1499 return result;
1500 }
1502 // Expansion didn't work, we'll try to do a Full GC.
1503 bool gc_succeeded = do_collection(false, /* explicit_gc */
1504 false, /* clear_all_soft_refs */
1505 word_size);
1506 if (!gc_succeeded) {
1507 *succeeded = false;
1508 return NULL;
1509 }
1511 // Retry the allocation
1512 result = attempt_allocation_at_safepoint(word_size,
1513 true /* expect_null_mutator_alloc_region */);
1514 if (result != NULL) {
1515 assert(*succeeded, "sanity");
1516 return result;
1517 }
1519 // Then, try a Full GC that will collect all soft references.
1520 gc_succeeded = do_collection(false, /* explicit_gc */
1521 true, /* clear_all_soft_refs */
1522 word_size);
1523 if (!gc_succeeded) {
1524 *succeeded = false;
1525 return NULL;
1526 }
1528 // Retry the allocation once more
1529 result = attempt_allocation_at_safepoint(word_size,
1530 true /* expect_null_mutator_alloc_region */);
1531 if (result != NULL) {
1532 assert(*succeeded, "sanity");
1533 return result;
1534 }
1536 assert(!collector_policy()->should_clear_all_soft_refs(),
1537 "Flag should have been handled and cleared prior to this point");
1539 // What else? We might try synchronous finalization later. If the total
1540 // space available is large enough for the allocation, then a more
1541 // complete compaction phase than we've tried so far might be
1542 // appropriate.
1543 assert(*succeeded, "sanity");
1544 return NULL;
1545 }
1547 // Attempting to expand the heap sufficiently
1548 // to support an allocation of the given "word_size". If
1549 // successful, perform the allocation and return the address of the
1550 // allocated block, or else "NULL".
1552 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1553 assert_at_safepoint(true /* should_be_vm_thread */);
1555 verify_region_sets_optional();
1557 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1558 if (expand(expand_bytes)) {
1559 verify_region_sets_optional();
1560 return attempt_allocation_at_safepoint(word_size,
1561 false /* expect_null_mutator_alloc_region */);
1562 }
1563 return NULL;
1564 }
1566 bool G1CollectedHeap::expand(size_t expand_bytes) {
1567 size_t old_mem_size = _g1_storage.committed_size();
1568 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1569 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1570 HeapRegion::GrainBytes);
1572 if (Verbose && PrintGC) {
1573 gclog_or_tty->print("Expanding garbage-first heap from %ldK by %ldK",
1574 old_mem_size/K, aligned_expand_bytes/K);
1575 }
1577 HeapWord* old_end = (HeapWord*)_g1_storage.high();
1578 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1579 if (successful) {
1580 HeapWord* new_end = (HeapWord*)_g1_storage.high();
1582 // Expand the committed region.
1583 _g1_committed.set_end(new_end);
1585 // Tell the cardtable about the expansion.
1586 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1588 // And the offset table as well.
1589 _bot_shared->resize(_g1_committed.word_size());
1591 expand_bytes = aligned_expand_bytes;
1592 HeapWord* base = old_end;
1594 // Create the heap regions for [old_end, new_end)
1595 while (expand_bytes > 0) {
1596 HeapWord* high = base + HeapRegion::GrainWords;
1598 // Create a new HeapRegion.
1599 MemRegion mr(base, high);
1600 bool is_zeroed = !_g1_max_committed.contains(base);
1601 HeapRegion* hr = new HeapRegion(_bot_shared, mr, is_zeroed);
1603 // Add it to the HeapRegionSeq.
1604 _hrs->insert(hr);
1605 _free_list.add_as_tail(hr);
1607 // And we used up an expansion region to create it.
1608 _expansion_regions--;
1610 expand_bytes -= HeapRegion::GrainBytes;
1611 base += HeapRegion::GrainWords;
1612 }
1613 assert(base == new_end, "sanity");
1615 // Now update max_committed if necessary.
1616 _g1_max_committed.set_end(MAX2(_g1_max_committed.end(), new_end));
1618 } else {
1619 // The expansion of the virtual storage space was unsuccessful.
1620 // Let's see if it was because we ran out of swap.
1621 if (G1ExitOnExpansionFailure &&
1622 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1623 // We had head room...
1624 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1625 }
1626 }
1628 if (Verbose && PrintGC) {
1629 size_t new_mem_size = _g1_storage.committed_size();
1630 gclog_or_tty->print_cr("...%s, expanded to %ldK",
1631 (successful ? "Successful" : "Failed"),
1632 new_mem_size/K);
1633 }
1634 return successful;
1635 }
1637 void G1CollectedHeap::shrink_helper(size_t shrink_bytes)
1638 {
1639 size_t old_mem_size = _g1_storage.committed_size();
1640 size_t aligned_shrink_bytes =
1641 ReservedSpace::page_align_size_down(shrink_bytes);
1642 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1643 HeapRegion::GrainBytes);
1644 size_t num_regions_deleted = 0;
1645 MemRegion mr = _hrs->shrink_by(aligned_shrink_bytes, num_regions_deleted);
1647 assert(mr.end() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1648 if (mr.byte_size() > 0)
1649 _g1_storage.shrink_by(mr.byte_size());
1650 assert(mr.start() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1652 _g1_committed.set_end(mr.start());
1653 _expansion_regions += num_regions_deleted;
1655 // Tell the cardtable about it.
1656 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1658 // And the offset table as well.
1659 _bot_shared->resize(_g1_committed.word_size());
1661 HeapRegionRemSet::shrink_heap(n_regions());
1663 if (Verbose && PrintGC) {
1664 size_t new_mem_size = _g1_storage.committed_size();
1665 gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
1666 old_mem_size/K, aligned_shrink_bytes/K,
1667 new_mem_size/K);
1668 }
1669 }
1671 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1672 verify_region_sets_optional();
1674 release_gc_alloc_regions(true /* totally */);
1675 // Instead of tearing down / rebuilding the free lists here, we
1676 // could instead use the remove_all_pending() method on free_list to
1677 // remove only the ones that we need to remove.
1678 tear_down_region_lists(); // We will rebuild them in a moment.
1679 shrink_helper(shrink_bytes);
1680 rebuild_region_lists();
1682 verify_region_sets_optional();
1683 }
1685 // Public methods.
1687 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1688 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1689 #endif // _MSC_VER
1692 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1693 SharedHeap(policy_),
1694 _g1_policy(policy_),
1695 _dirty_card_queue_set(false),
1696 _into_cset_dirty_card_queue_set(false),
1697 _is_alive_closure(this),
1698 _ref_processor(NULL),
1699 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1700 _bot_shared(NULL),
1701 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1702 _evac_failure_scan_stack(NULL) ,
1703 _mark_in_progress(false),
1704 _cg1r(NULL), _summary_bytes_used(0),
1705 _refine_cte_cl(NULL),
1706 _full_collection(false),
1707 _free_list("Master Free List"),
1708 _secondary_free_list("Secondary Free List"),
1709 _humongous_set("Master Humongous Set"),
1710 _free_regions_coming(false),
1711 _young_list(new YoungList(this)),
1712 _gc_time_stamp(0),
1713 _surviving_young_words(NULL),
1714 _full_collections_completed(0),
1715 _in_cset_fast_test(NULL),
1716 _in_cset_fast_test_base(NULL),
1717 _dirty_cards_region_list(NULL) {
1718 _g1h = this; // To catch bugs.
1719 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1720 vm_exit_during_initialization("Failed necessary allocation.");
1721 }
1723 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1725 int n_queues = MAX2((int)ParallelGCThreads, 1);
1726 _task_queues = new RefToScanQueueSet(n_queues);
1728 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1729 assert(n_rem_sets > 0, "Invariant.");
1731 HeapRegionRemSetIterator** iter_arr =
1732 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1733 for (int i = 0; i < n_queues; i++) {
1734 iter_arr[i] = new HeapRegionRemSetIterator();
1735 }
1736 _rem_set_iterator = iter_arr;
1738 for (int i = 0; i < n_queues; i++) {
1739 RefToScanQueue* q = new RefToScanQueue();
1740 q->initialize();
1741 _task_queues->register_queue(i, q);
1742 }
1744 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1745 _gc_alloc_regions[ap] = NULL;
1746 _gc_alloc_region_counts[ap] = 0;
1747 _retained_gc_alloc_regions[ap] = NULL;
1748 // by default, we do not retain a GC alloc region for each ap;
1749 // we'll override this, when appropriate, below
1750 _retain_gc_alloc_region[ap] = false;
1751 }
1753 // We will try to remember the last half-full tenured region we
1754 // allocated to at the end of a collection so that we can re-use it
1755 // during the next collection.
1756 _retain_gc_alloc_region[GCAllocForTenured] = true;
1758 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1759 }
1761 jint G1CollectedHeap::initialize() {
1762 CollectedHeap::pre_initialize();
1763 os::enable_vtime();
1765 // Necessary to satisfy locking discipline assertions.
1767 MutexLocker x(Heap_lock);
1769 // While there are no constraints in the GC code that HeapWordSize
1770 // be any particular value, there are multiple other areas in the
1771 // system which believe this to be true (e.g. oop->object_size in some
1772 // cases incorrectly returns the size in wordSize units rather than
1773 // HeapWordSize).
1774 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1776 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1777 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1779 // Ensure that the sizes are properly aligned.
1780 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1781 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1783 _cg1r = new ConcurrentG1Refine();
1785 // Reserve the maximum.
1786 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1787 // Includes the perm-gen.
1789 const size_t total_reserved = max_byte_size + pgs->max_size();
1790 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1792 ReservedSpace heap_rs(max_byte_size + pgs->max_size(),
1793 HeapRegion::GrainBytes,
1794 UseLargePages, addr);
1796 if (UseCompressedOops) {
1797 if (addr != NULL && !heap_rs.is_reserved()) {
1798 // Failed to reserve at specified address - the requested memory
1799 // region is taken already, for example, by 'java' launcher.
1800 // Try again to reserver heap higher.
1801 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
1802 ReservedSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
1803 UseLargePages, addr);
1804 if (addr != NULL && !heap_rs0.is_reserved()) {
1805 // Failed to reserve at specified address again - give up.
1806 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
1807 assert(addr == NULL, "");
1808 ReservedSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
1809 UseLargePages, addr);
1810 heap_rs = heap_rs1;
1811 } else {
1812 heap_rs = heap_rs0;
1813 }
1814 }
1815 }
1817 if (!heap_rs.is_reserved()) {
1818 vm_exit_during_initialization("Could not reserve enough space for object heap");
1819 return JNI_ENOMEM;
1820 }
1822 // It is important to do this in a way such that concurrent readers can't
1823 // temporarily think somethings in the heap. (I've actually seen this
1824 // happen in asserts: DLD.)
1825 _reserved.set_word_size(0);
1826 _reserved.set_start((HeapWord*)heap_rs.base());
1827 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1829 _expansion_regions = max_byte_size/HeapRegion::GrainBytes;
1831 // Create the gen rem set (and barrier set) for the entire reserved region.
1832 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1833 set_barrier_set(rem_set()->bs());
1834 if (barrier_set()->is_a(BarrierSet::ModRef)) {
1835 _mr_bs = (ModRefBarrierSet*)_barrier_set;
1836 } else {
1837 vm_exit_during_initialization("G1 requires a mod ref bs.");
1838 return JNI_ENOMEM;
1839 }
1841 // Also create a G1 rem set.
1842 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
1843 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
1844 } else {
1845 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
1846 return JNI_ENOMEM;
1847 }
1849 // Carve out the G1 part of the heap.
1851 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1852 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
1853 g1_rs.size()/HeapWordSize);
1854 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
1856 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
1858 _g1_storage.initialize(g1_rs, 0);
1859 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
1860 _g1_max_committed = _g1_committed;
1861 _hrs = new HeapRegionSeq(_expansion_regions);
1862 guarantee(_hrs != NULL, "Couldn't allocate HeapRegionSeq");
1864 // 6843694 - ensure that the maximum region index can fit
1865 // in the remembered set structures.
1866 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1867 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1869 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1870 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1871 guarantee((size_t) HeapRegion::CardsPerRegion < max_cards_per_region,
1872 "too many cards per region");
1874 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
1876 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
1877 heap_word_size(init_byte_size));
1879 _g1h = this;
1881 _in_cset_fast_test_length = max_regions();
1882 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length);
1884 // We're biasing _in_cset_fast_test to avoid subtracting the
1885 // beginning of the heap every time we want to index; basically
1886 // it's the same with what we do with the card table.
1887 _in_cset_fast_test = _in_cset_fast_test_base -
1888 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
1890 // Clear the _cset_fast_test bitmap in anticipation of adding
1891 // regions to the incremental collection set for the first
1892 // evacuation pause.
1893 clear_cset_fast_test();
1895 // Create the ConcurrentMark data structure and thread.
1896 // (Must do this late, so that "max_regions" is defined.)
1897 _cm = new ConcurrentMark(heap_rs, (int) max_regions());
1898 _cmThread = _cm->cmThread();
1900 // Initialize the from_card cache structure of HeapRegionRemSet.
1901 HeapRegionRemSet::init_heap(max_regions());
1903 // Now expand into the initial heap size.
1904 if (!expand(init_byte_size)) {
1905 vm_exit_during_initialization("Failed to allocate initial heap.");
1906 return JNI_ENOMEM;
1907 }
1909 // Perform any initialization actions delegated to the policy.
1910 g1_policy()->init();
1912 g1_policy()->note_start_of_mark_thread();
1914 _refine_cte_cl =
1915 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
1916 g1_rem_set(),
1917 concurrent_g1_refine());
1918 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
1920 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1921 SATB_Q_FL_lock,
1922 G1SATBProcessCompletedThreshold,
1923 Shared_SATB_Q_lock);
1925 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1926 DirtyCardQ_FL_lock,
1927 concurrent_g1_refine()->yellow_zone(),
1928 concurrent_g1_refine()->red_zone(),
1929 Shared_DirtyCardQ_lock);
1931 if (G1DeferredRSUpdate) {
1932 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1933 DirtyCardQ_FL_lock,
1934 -1, // never trigger processing
1935 -1, // no limit on length
1936 Shared_DirtyCardQ_lock,
1937 &JavaThread::dirty_card_queue_set());
1938 }
1940 // Initialize the card queue set used to hold cards containing
1941 // references into the collection set.
1942 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
1943 DirtyCardQ_FL_lock,
1944 -1, // never trigger processing
1945 -1, // no limit on length
1946 Shared_DirtyCardQ_lock,
1947 &JavaThread::dirty_card_queue_set());
1949 // In case we're keeping closure specialization stats, initialize those
1950 // counts and that mechanism.
1951 SpecializationStats::clear();
1953 _gc_alloc_region_list = NULL;
1955 // Do later initialization work for concurrent refinement.
1956 _cg1r->init();
1958 // Here we allocate the dummy full region that is required by the
1959 // G1AllocRegion class. If we don't pass an address in the reserved
1960 // space here, lots of asserts fire.
1961 MemRegion mr(_g1_reserved.start(), HeapRegion::GrainWords);
1962 HeapRegion* dummy_region = new HeapRegion(_bot_shared, mr, true);
1963 // We'll re-use the same region whether the alloc region will
1964 // require BOT updates or not and, if it doesn't, then a non-young
1965 // region will complain that it cannot support allocations without
1966 // BOT updates. So we'll tag the dummy region as young to avoid that.
1967 dummy_region->set_young();
1968 // Make sure it's full.
1969 dummy_region->set_top(dummy_region->end());
1970 G1AllocRegion::setup(this, dummy_region);
1972 init_mutator_alloc_region();
1974 return JNI_OK;
1975 }
1977 void G1CollectedHeap::ref_processing_init() {
1978 // Reference processing in G1 currently works as follows:
1979 //
1980 // * There is only one reference processor instance that
1981 // 'spans' the entire heap. It is created by the code
1982 // below.
1983 // * Reference discovery is not enabled during an incremental
1984 // pause (see 6484982).
1985 // * Discoverered refs are not enqueued nor are they processed
1986 // during an incremental pause (see 6484982).
1987 // * Reference discovery is enabled at initial marking.
1988 // * Reference discovery is disabled and the discovered
1989 // references processed etc during remarking.
1990 // * Reference discovery is MT (see below).
1991 // * Reference discovery requires a barrier (see below).
1992 // * Reference processing is currently not MT (see 6608385).
1993 // * A full GC enables (non-MT) reference discovery and
1994 // processes any discovered references.
1996 SharedHeap::ref_processing_init();
1997 MemRegion mr = reserved_region();
1998 _ref_processor =
1999 new ReferenceProcessor(mr, // span
2000 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
2001 (int) ParallelGCThreads, // degree of mt processing
2002 ParallelGCThreads > 1 || ConcGCThreads > 1, // mt discovery
2003 (int) MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery
2004 false, // Reference discovery is not atomic
2005 &_is_alive_closure, // is alive closure for efficiency
2006 true); // Setting next fields of discovered
2007 // lists requires a barrier.
2008 }
2010 size_t G1CollectedHeap::capacity() const {
2011 return _g1_committed.byte_size();
2012 }
2014 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2015 DirtyCardQueue* into_cset_dcq,
2016 bool concurrent,
2017 int worker_i) {
2018 // Clean cards in the hot card cache
2019 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2021 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2022 int n_completed_buffers = 0;
2023 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2024 n_completed_buffers++;
2025 }
2026 g1_policy()->record_update_rs_processed_buffers(worker_i,
2027 (double) n_completed_buffers);
2028 dcqs.clear_n_completed_buffers();
2029 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2030 }
2033 // Computes the sum of the storage used by the various regions.
2035 size_t G1CollectedHeap::used() const {
2036 assert(Heap_lock->owner() != NULL,
2037 "Should be owned on this thread's behalf.");
2038 size_t result = _summary_bytes_used;
2039 // Read only once in case it is set to NULL concurrently
2040 HeapRegion* hr = _mutator_alloc_region.get();
2041 if (hr != NULL)
2042 result += hr->used();
2043 return result;
2044 }
2046 size_t G1CollectedHeap::used_unlocked() const {
2047 size_t result = _summary_bytes_used;
2048 return result;
2049 }
2051 class SumUsedClosure: public HeapRegionClosure {
2052 size_t _used;
2053 public:
2054 SumUsedClosure() : _used(0) {}
2055 bool doHeapRegion(HeapRegion* r) {
2056 if (!r->continuesHumongous()) {
2057 _used += r->used();
2058 }
2059 return false;
2060 }
2061 size_t result() { return _used; }
2062 };
2064 size_t G1CollectedHeap::recalculate_used() const {
2065 SumUsedClosure blk;
2066 _hrs->iterate(&blk);
2067 return blk.result();
2068 }
2070 #ifndef PRODUCT
2071 class SumUsedRegionsClosure: public HeapRegionClosure {
2072 size_t _num;
2073 public:
2074 SumUsedRegionsClosure() : _num(0) {}
2075 bool doHeapRegion(HeapRegion* r) {
2076 if (r->continuesHumongous() || r->used() > 0 || r->is_gc_alloc_region()) {
2077 _num += 1;
2078 }
2079 return false;
2080 }
2081 size_t result() { return _num; }
2082 };
2084 size_t G1CollectedHeap::recalculate_used_regions() const {
2085 SumUsedRegionsClosure blk;
2086 _hrs->iterate(&blk);
2087 return blk.result();
2088 }
2089 #endif // PRODUCT
2091 size_t G1CollectedHeap::unsafe_max_alloc() {
2092 if (free_regions() > 0) return HeapRegion::GrainBytes;
2093 // otherwise, is there space in the current allocation region?
2095 // We need to store the current allocation region in a local variable
2096 // here. The problem is that this method doesn't take any locks and
2097 // there may be other threads which overwrite the current allocation
2098 // region field. attempt_allocation(), for example, sets it to NULL
2099 // and this can happen *after* the NULL check here but before the call
2100 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2101 // to be a problem in the optimized build, since the two loads of the
2102 // current allocation region field are optimized away.
2103 HeapRegion* hr = _mutator_alloc_region.get();
2104 if (hr == NULL) {
2105 return 0;
2106 }
2107 return hr->free();
2108 }
2110 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2111 return
2112 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
2113 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
2114 }
2116 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2117 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2119 // We assume that if concurrent == true, then the caller is a
2120 // concurrent thread that was joined the Suspendible Thread
2121 // Set. If there's ever a cheap way to check this, we should add an
2122 // assert here.
2124 // We have already incremented _total_full_collections at the start
2125 // of the GC, so total_full_collections() represents how many full
2126 // collections have been started.
2127 unsigned int full_collections_started = total_full_collections();
2129 // Given that this method is called at the end of a Full GC or of a
2130 // concurrent cycle, and those can be nested (i.e., a Full GC can
2131 // interrupt a concurrent cycle), the number of full collections
2132 // completed should be either one (in the case where there was no
2133 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2134 // behind the number of full collections started.
2136 // This is the case for the inner caller, i.e. a Full GC.
2137 assert(concurrent ||
2138 (full_collections_started == _full_collections_completed + 1) ||
2139 (full_collections_started == _full_collections_completed + 2),
2140 err_msg("for inner caller (Full GC): full_collections_started = %u "
2141 "is inconsistent with _full_collections_completed = %u",
2142 full_collections_started, _full_collections_completed));
2144 // This is the case for the outer caller, i.e. the concurrent cycle.
2145 assert(!concurrent ||
2146 (full_collections_started == _full_collections_completed + 1),
2147 err_msg("for outer caller (concurrent cycle): "
2148 "full_collections_started = %u "
2149 "is inconsistent with _full_collections_completed = %u",
2150 full_collections_started, _full_collections_completed));
2152 _full_collections_completed += 1;
2154 // We need to clear the "in_progress" flag in the CM thread before
2155 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2156 // is set) so that if a waiter requests another System.gc() it doesn't
2157 // incorrectly see that a marking cyle is still in progress.
2158 if (concurrent) {
2159 _cmThread->clear_in_progress();
2160 }
2162 // This notify_all() will ensure that a thread that called
2163 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2164 // and it's waiting for a full GC to finish will be woken up. It is
2165 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2166 FullGCCount_lock->notify_all();
2167 }
2169 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2170 assert_at_safepoint(true /* should_be_vm_thread */);
2171 GCCauseSetter gcs(this, cause);
2172 switch (cause) {
2173 case GCCause::_heap_inspection:
2174 case GCCause::_heap_dump: {
2175 HandleMark hm;
2176 do_full_collection(false); // don't clear all soft refs
2177 break;
2178 }
2179 default: // XXX FIX ME
2180 ShouldNotReachHere(); // Unexpected use of this function
2181 }
2182 }
2184 void G1CollectedHeap::collect(GCCause::Cause cause) {
2185 // The caller doesn't have the Heap_lock
2186 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
2188 unsigned int gc_count_before;
2189 unsigned int full_gc_count_before;
2190 {
2191 MutexLocker ml(Heap_lock);
2193 // Read the GC count while holding the Heap_lock
2194 gc_count_before = SharedHeap::heap()->total_collections();
2195 full_gc_count_before = SharedHeap::heap()->total_full_collections();
2196 }
2198 if (should_do_concurrent_full_gc(cause)) {
2199 // Schedule an initial-mark evacuation pause that will start a
2200 // concurrent cycle. We're setting word_size to 0 which means that
2201 // we are not requesting a post-GC allocation.
2202 VM_G1IncCollectionPause op(gc_count_before,
2203 0, /* word_size */
2204 true, /* should_initiate_conc_mark */
2205 g1_policy()->max_pause_time_ms(),
2206 cause);
2207 VMThread::execute(&op);
2208 } else {
2209 if (cause == GCCause::_gc_locker
2210 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2212 // Schedule a standard evacuation pause. We're setting word_size
2213 // to 0 which means that we are not requesting a post-GC allocation.
2214 VM_G1IncCollectionPause op(gc_count_before,
2215 0, /* word_size */
2216 false, /* should_initiate_conc_mark */
2217 g1_policy()->max_pause_time_ms(),
2218 cause);
2219 VMThread::execute(&op);
2220 } else {
2221 // Schedule a Full GC.
2222 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2223 VMThread::execute(&op);
2224 }
2225 }
2226 }
2228 bool G1CollectedHeap::is_in(const void* p) const {
2229 if (_g1_committed.contains(p)) {
2230 HeapRegion* hr = _hrs->addr_to_region(p);
2231 return hr->is_in(p);
2232 } else {
2233 return _perm_gen->as_gen()->is_in(p);
2234 }
2235 }
2237 // Iteration functions.
2239 // Iterates an OopClosure over all ref-containing fields of objects
2240 // within a HeapRegion.
2242 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2243 MemRegion _mr;
2244 OopClosure* _cl;
2245 public:
2246 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2247 : _mr(mr), _cl(cl) {}
2248 bool doHeapRegion(HeapRegion* r) {
2249 if (! r->continuesHumongous()) {
2250 r->oop_iterate(_cl);
2251 }
2252 return false;
2253 }
2254 };
2256 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2257 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2258 _hrs->iterate(&blk);
2259 if (do_perm) {
2260 perm_gen()->oop_iterate(cl);
2261 }
2262 }
2264 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2265 IterateOopClosureRegionClosure blk(mr, cl);
2266 _hrs->iterate(&blk);
2267 if (do_perm) {
2268 perm_gen()->oop_iterate(cl);
2269 }
2270 }
2272 // Iterates an ObjectClosure over all objects within a HeapRegion.
2274 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2275 ObjectClosure* _cl;
2276 public:
2277 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2278 bool doHeapRegion(HeapRegion* r) {
2279 if (! r->continuesHumongous()) {
2280 r->object_iterate(_cl);
2281 }
2282 return false;
2283 }
2284 };
2286 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2287 IterateObjectClosureRegionClosure blk(cl);
2288 _hrs->iterate(&blk);
2289 if (do_perm) {
2290 perm_gen()->object_iterate(cl);
2291 }
2292 }
2294 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2295 // FIXME: is this right?
2296 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2297 }
2299 // Calls a SpaceClosure on a HeapRegion.
2301 class SpaceClosureRegionClosure: public HeapRegionClosure {
2302 SpaceClosure* _cl;
2303 public:
2304 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2305 bool doHeapRegion(HeapRegion* r) {
2306 _cl->do_space(r);
2307 return false;
2308 }
2309 };
2311 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2312 SpaceClosureRegionClosure blk(cl);
2313 _hrs->iterate(&blk);
2314 }
2316 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) {
2317 _hrs->iterate(cl);
2318 }
2320 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2321 HeapRegionClosure* cl) {
2322 _hrs->iterate_from(r, cl);
2323 }
2325 void
2326 G1CollectedHeap::heap_region_iterate_from(int idx, HeapRegionClosure* cl) {
2327 _hrs->iterate_from(idx, cl);
2328 }
2330 HeapRegion* G1CollectedHeap::region_at(size_t idx) { return _hrs->at(idx); }
2332 void
2333 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2334 int worker,
2335 jint claim_value) {
2336 const size_t regions = n_regions();
2337 const size_t worker_num = (G1CollectedHeap::use_parallel_gc_threads() ? ParallelGCThreads : 1);
2338 // try to spread out the starting points of the workers
2339 const size_t start_index = regions / worker_num * (size_t) worker;
2341 // each worker will actually look at all regions
2342 for (size_t count = 0; count < regions; ++count) {
2343 const size_t index = (start_index + count) % regions;
2344 assert(0 <= index && index < regions, "sanity");
2345 HeapRegion* r = region_at(index);
2346 // we'll ignore "continues humongous" regions (we'll process them
2347 // when we come across their corresponding "start humongous"
2348 // region) and regions already claimed
2349 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2350 continue;
2351 }
2352 // OK, try to claim it
2353 if (r->claimHeapRegion(claim_value)) {
2354 // success!
2355 assert(!r->continuesHumongous(), "sanity");
2356 if (r->startsHumongous()) {
2357 // If the region is "starts humongous" we'll iterate over its
2358 // "continues humongous" first; in fact we'll do them
2359 // first. The order is important. In on case, calling the
2360 // closure on the "starts humongous" region might de-allocate
2361 // and clear all its "continues humongous" regions and, as a
2362 // result, we might end up processing them twice. So, we'll do
2363 // them first (notice: most closures will ignore them anyway) and
2364 // then we'll do the "starts humongous" region.
2365 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) {
2366 HeapRegion* chr = region_at(ch_index);
2368 // if the region has already been claimed or it's not
2369 // "continues humongous" we're done
2370 if (chr->claim_value() == claim_value ||
2371 !chr->continuesHumongous()) {
2372 break;
2373 }
2375 // Noone should have claimed it directly. We can given
2376 // that we claimed its "starts humongous" region.
2377 assert(chr->claim_value() != claim_value, "sanity");
2378 assert(chr->humongous_start_region() == r, "sanity");
2380 if (chr->claimHeapRegion(claim_value)) {
2381 // we should always be able to claim it; noone else should
2382 // be trying to claim this region
2384 bool res2 = cl->doHeapRegion(chr);
2385 assert(!res2, "Should not abort");
2387 // Right now, this holds (i.e., no closure that actually
2388 // does something with "continues humongous" regions
2389 // clears them). We might have to weaken it in the future,
2390 // but let's leave these two asserts here for extra safety.
2391 assert(chr->continuesHumongous(), "should still be the case");
2392 assert(chr->humongous_start_region() == r, "sanity");
2393 } else {
2394 guarantee(false, "we should not reach here");
2395 }
2396 }
2397 }
2399 assert(!r->continuesHumongous(), "sanity");
2400 bool res = cl->doHeapRegion(r);
2401 assert(!res, "Should not abort");
2402 }
2403 }
2404 }
2406 class ResetClaimValuesClosure: public HeapRegionClosure {
2407 public:
2408 bool doHeapRegion(HeapRegion* r) {
2409 r->set_claim_value(HeapRegion::InitialClaimValue);
2410 return false;
2411 }
2412 };
2414 void
2415 G1CollectedHeap::reset_heap_region_claim_values() {
2416 ResetClaimValuesClosure blk;
2417 heap_region_iterate(&blk);
2418 }
2420 #ifdef ASSERT
2421 // This checks whether all regions in the heap have the correct claim
2422 // value. I also piggy-backed on this a check to ensure that the
2423 // humongous_start_region() information on "continues humongous"
2424 // regions is correct.
2426 class CheckClaimValuesClosure : public HeapRegionClosure {
2427 private:
2428 jint _claim_value;
2429 size_t _failures;
2430 HeapRegion* _sh_region;
2431 public:
2432 CheckClaimValuesClosure(jint claim_value) :
2433 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2434 bool doHeapRegion(HeapRegion* r) {
2435 if (r->claim_value() != _claim_value) {
2436 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2437 "claim value = %d, should be %d",
2438 r->bottom(), r->end(), r->claim_value(),
2439 _claim_value);
2440 ++_failures;
2441 }
2442 if (!r->isHumongous()) {
2443 _sh_region = NULL;
2444 } else if (r->startsHumongous()) {
2445 _sh_region = r;
2446 } else if (r->continuesHumongous()) {
2447 if (r->humongous_start_region() != _sh_region) {
2448 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2449 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2450 r->bottom(), r->end(),
2451 r->humongous_start_region(),
2452 _sh_region);
2453 ++_failures;
2454 }
2455 }
2456 return false;
2457 }
2458 size_t failures() {
2459 return _failures;
2460 }
2461 };
2463 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2464 CheckClaimValuesClosure cl(claim_value);
2465 heap_region_iterate(&cl);
2466 return cl.failures() == 0;
2467 }
2468 #endif // ASSERT
2470 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2471 HeapRegion* r = g1_policy()->collection_set();
2472 while (r != NULL) {
2473 HeapRegion* next = r->next_in_collection_set();
2474 if (cl->doHeapRegion(r)) {
2475 cl->incomplete();
2476 return;
2477 }
2478 r = next;
2479 }
2480 }
2482 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2483 HeapRegionClosure *cl) {
2484 if (r == NULL) {
2485 // The CSet is empty so there's nothing to do.
2486 return;
2487 }
2489 assert(r->in_collection_set(),
2490 "Start region must be a member of the collection set.");
2491 HeapRegion* cur = r;
2492 while (cur != NULL) {
2493 HeapRegion* next = cur->next_in_collection_set();
2494 if (cl->doHeapRegion(cur) && false) {
2495 cl->incomplete();
2496 return;
2497 }
2498 cur = next;
2499 }
2500 cur = g1_policy()->collection_set();
2501 while (cur != r) {
2502 HeapRegion* next = cur->next_in_collection_set();
2503 if (cl->doHeapRegion(cur) && false) {
2504 cl->incomplete();
2505 return;
2506 }
2507 cur = next;
2508 }
2509 }
2511 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2512 return _hrs->length() > 0 ? _hrs->at(0) : NULL;
2513 }
2516 Space* G1CollectedHeap::space_containing(const void* addr) const {
2517 Space* res = heap_region_containing(addr);
2518 if (res == NULL)
2519 res = perm_gen()->space_containing(addr);
2520 return res;
2521 }
2523 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2524 Space* sp = space_containing(addr);
2525 if (sp != NULL) {
2526 return sp->block_start(addr);
2527 }
2528 return NULL;
2529 }
2531 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2532 Space* sp = space_containing(addr);
2533 assert(sp != NULL, "block_size of address outside of heap");
2534 return sp->block_size(addr);
2535 }
2537 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2538 Space* sp = space_containing(addr);
2539 return sp->block_is_obj(addr);
2540 }
2542 bool G1CollectedHeap::supports_tlab_allocation() const {
2543 return true;
2544 }
2546 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2547 return HeapRegion::GrainBytes;
2548 }
2550 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2551 // Return the remaining space in the cur alloc region, but not less than
2552 // the min TLAB size.
2554 // Also, this value can be at most the humongous object threshold,
2555 // since we can't allow tlabs to grow big enough to accomodate
2556 // humongous objects.
2558 HeapRegion* hr = _mutator_alloc_region.get();
2559 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2560 if (hr == NULL) {
2561 return max_tlab_size;
2562 } else {
2563 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2564 }
2565 }
2567 size_t G1CollectedHeap::large_typearray_limit() {
2568 // FIXME
2569 return HeapRegion::GrainBytes/HeapWordSize;
2570 }
2572 size_t G1CollectedHeap::max_capacity() const {
2573 return _g1_reserved.byte_size();
2574 }
2576 jlong G1CollectedHeap::millis_since_last_gc() {
2577 // assert(false, "NYI");
2578 return 0;
2579 }
2581 void G1CollectedHeap::prepare_for_verify() {
2582 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2583 ensure_parsability(false);
2584 }
2585 g1_rem_set()->prepare_for_verify();
2586 }
2588 class VerifyLivenessOopClosure: public OopClosure {
2589 G1CollectedHeap* g1h;
2590 public:
2591 VerifyLivenessOopClosure(G1CollectedHeap* _g1h) {
2592 g1h = _g1h;
2593 }
2594 void do_oop(narrowOop *p) { do_oop_work(p); }
2595 void do_oop( oop *p) { do_oop_work(p); }
2597 template <class T> void do_oop_work(T *p) {
2598 oop obj = oopDesc::load_decode_heap_oop(p);
2599 guarantee(obj == NULL || !g1h->is_obj_dead(obj),
2600 "Dead object referenced by a not dead object");
2601 }
2602 };
2604 class VerifyObjsInRegionClosure: public ObjectClosure {
2605 private:
2606 G1CollectedHeap* _g1h;
2607 size_t _live_bytes;
2608 HeapRegion *_hr;
2609 bool _use_prev_marking;
2610 public:
2611 // use_prev_marking == true -> use "prev" marking information,
2612 // use_prev_marking == false -> use "next" marking information
2613 VerifyObjsInRegionClosure(HeapRegion *hr, bool use_prev_marking)
2614 : _live_bytes(0), _hr(hr), _use_prev_marking(use_prev_marking) {
2615 _g1h = G1CollectedHeap::heap();
2616 }
2617 void do_object(oop o) {
2618 VerifyLivenessOopClosure isLive(_g1h);
2619 assert(o != NULL, "Huh?");
2620 if (!_g1h->is_obj_dead_cond(o, _use_prev_marking)) {
2621 o->oop_iterate(&isLive);
2622 if (!_hr->obj_allocated_since_prev_marking(o)) {
2623 size_t obj_size = o->size(); // Make sure we don't overflow
2624 _live_bytes += (obj_size * HeapWordSize);
2625 }
2626 }
2627 }
2628 size_t live_bytes() { return _live_bytes; }
2629 };
2631 class PrintObjsInRegionClosure : public ObjectClosure {
2632 HeapRegion *_hr;
2633 G1CollectedHeap *_g1;
2634 public:
2635 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2636 _g1 = G1CollectedHeap::heap();
2637 };
2639 void do_object(oop o) {
2640 if (o != NULL) {
2641 HeapWord *start = (HeapWord *) o;
2642 size_t word_sz = o->size();
2643 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2644 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2645 (void*) o, word_sz,
2646 _g1->isMarkedPrev(o),
2647 _g1->isMarkedNext(o),
2648 _hr->obj_allocated_since_prev_marking(o));
2649 HeapWord *end = start + word_sz;
2650 HeapWord *cur;
2651 int *val;
2652 for (cur = start; cur < end; cur++) {
2653 val = (int *) cur;
2654 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
2655 }
2656 }
2657 }
2658 };
2660 class VerifyRegionClosure: public HeapRegionClosure {
2661 private:
2662 bool _allow_dirty;
2663 bool _par;
2664 bool _use_prev_marking;
2665 bool _failures;
2666 public:
2667 // use_prev_marking == true -> use "prev" marking information,
2668 // use_prev_marking == false -> use "next" marking information
2669 VerifyRegionClosure(bool allow_dirty, bool par, bool use_prev_marking)
2670 : _allow_dirty(allow_dirty),
2671 _par(par),
2672 _use_prev_marking(use_prev_marking),
2673 _failures(false) {}
2675 bool failures() {
2676 return _failures;
2677 }
2679 bool doHeapRegion(HeapRegion* r) {
2680 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
2681 "Should be unclaimed at verify points.");
2682 if (!r->continuesHumongous()) {
2683 bool failures = false;
2684 r->verify(_allow_dirty, _use_prev_marking, &failures);
2685 if (failures) {
2686 _failures = true;
2687 } else {
2688 VerifyObjsInRegionClosure not_dead_yet_cl(r, _use_prev_marking);
2689 r->object_iterate(¬_dead_yet_cl);
2690 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2691 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2692 "max_live_bytes "SIZE_FORMAT" "
2693 "< calculated "SIZE_FORMAT,
2694 r->bottom(), r->end(),
2695 r->max_live_bytes(),
2696 not_dead_yet_cl.live_bytes());
2697 _failures = true;
2698 }
2699 }
2700 }
2701 return false; // stop the region iteration if we hit a failure
2702 }
2703 };
2705 class VerifyRootsClosure: public OopsInGenClosure {
2706 private:
2707 G1CollectedHeap* _g1h;
2708 bool _use_prev_marking;
2709 bool _failures;
2710 public:
2711 // use_prev_marking == true -> use "prev" marking information,
2712 // use_prev_marking == false -> use "next" marking information
2713 VerifyRootsClosure(bool use_prev_marking) :
2714 _g1h(G1CollectedHeap::heap()),
2715 _use_prev_marking(use_prev_marking),
2716 _failures(false) { }
2718 bool failures() { return _failures; }
2720 template <class T> void do_oop_nv(T* p) {
2721 T heap_oop = oopDesc::load_heap_oop(p);
2722 if (!oopDesc::is_null(heap_oop)) {
2723 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2724 if (_g1h->is_obj_dead_cond(obj, _use_prev_marking)) {
2725 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2726 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2727 obj->print_on(gclog_or_tty);
2728 _failures = true;
2729 }
2730 }
2731 }
2733 void do_oop(oop* p) { do_oop_nv(p); }
2734 void do_oop(narrowOop* p) { do_oop_nv(p); }
2735 };
2737 // This is the task used for parallel heap verification.
2739 class G1ParVerifyTask: public AbstractGangTask {
2740 private:
2741 G1CollectedHeap* _g1h;
2742 bool _allow_dirty;
2743 bool _use_prev_marking;
2744 bool _failures;
2746 public:
2747 // use_prev_marking == true -> use "prev" marking information,
2748 // use_prev_marking == false -> use "next" marking information
2749 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty,
2750 bool use_prev_marking) :
2751 AbstractGangTask("Parallel verify task"),
2752 _g1h(g1h),
2753 _allow_dirty(allow_dirty),
2754 _use_prev_marking(use_prev_marking),
2755 _failures(false) { }
2757 bool failures() {
2758 return _failures;
2759 }
2761 void work(int worker_i) {
2762 HandleMark hm;
2763 VerifyRegionClosure blk(_allow_dirty, true, _use_prev_marking);
2764 _g1h->heap_region_par_iterate_chunked(&blk, worker_i,
2765 HeapRegion::ParVerifyClaimValue);
2766 if (blk.failures()) {
2767 _failures = true;
2768 }
2769 }
2770 };
2772 void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
2773 verify(allow_dirty, silent, /* use_prev_marking */ true);
2774 }
2776 void G1CollectedHeap::verify(bool allow_dirty,
2777 bool silent,
2778 bool use_prev_marking) {
2779 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2780 if (!silent) { gclog_or_tty->print("roots "); }
2781 VerifyRootsClosure rootsCl(use_prev_marking);
2782 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
2783 process_strong_roots(true, // activate StrongRootsScope
2784 false,
2785 SharedHeap::SO_AllClasses,
2786 &rootsCl,
2787 &blobsCl,
2788 &rootsCl);
2789 bool failures = rootsCl.failures();
2790 rem_set()->invalidate(perm_gen()->used_region(), false);
2791 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
2792 verify_region_sets();
2793 if (!silent) { gclog_or_tty->print("HeapRegions "); }
2794 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
2795 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
2796 "sanity check");
2798 G1ParVerifyTask task(this, allow_dirty, use_prev_marking);
2799 int n_workers = workers()->total_workers();
2800 set_par_threads(n_workers);
2801 workers()->run_task(&task);
2802 set_par_threads(0);
2803 if (task.failures()) {
2804 failures = true;
2805 }
2807 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
2808 "sanity check");
2810 reset_heap_region_claim_values();
2812 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
2813 "sanity check");
2814 } else {
2815 VerifyRegionClosure blk(allow_dirty, false, use_prev_marking);
2816 _hrs->iterate(&blk);
2817 if (blk.failures()) {
2818 failures = true;
2819 }
2820 }
2821 if (!silent) gclog_or_tty->print("RemSet ");
2822 rem_set()->verify();
2824 if (failures) {
2825 gclog_or_tty->print_cr("Heap:");
2826 print_on(gclog_or_tty, true /* extended */);
2827 gclog_or_tty->print_cr("");
2828 #ifndef PRODUCT
2829 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
2830 concurrent_mark()->print_reachable("at-verification-failure",
2831 use_prev_marking, false /* all */);
2832 }
2833 #endif
2834 gclog_or_tty->flush();
2835 }
2836 guarantee(!failures, "there should not have been any failures");
2837 } else {
2838 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
2839 }
2840 }
2842 class PrintRegionClosure: public HeapRegionClosure {
2843 outputStream* _st;
2844 public:
2845 PrintRegionClosure(outputStream* st) : _st(st) {}
2846 bool doHeapRegion(HeapRegion* r) {
2847 r->print_on(_st);
2848 return false;
2849 }
2850 };
2852 void G1CollectedHeap::print() const { print_on(tty); }
2854 void G1CollectedHeap::print_on(outputStream* st) const {
2855 print_on(st, PrintHeapAtGCExtended);
2856 }
2858 void G1CollectedHeap::print_on(outputStream* st, bool extended) const {
2859 st->print(" %-20s", "garbage-first heap");
2860 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2861 capacity()/K, used_unlocked()/K);
2862 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
2863 _g1_storage.low_boundary(),
2864 _g1_storage.high(),
2865 _g1_storage.high_boundary());
2866 st->cr();
2867 st->print(" region size " SIZE_FORMAT "K, ",
2868 HeapRegion::GrainBytes/K);
2869 size_t young_regions = _young_list->length();
2870 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
2871 young_regions, young_regions * HeapRegion::GrainBytes / K);
2872 size_t survivor_regions = g1_policy()->recorded_survivor_regions();
2873 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
2874 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
2875 st->cr();
2876 perm()->as_gen()->print_on(st);
2877 if (extended) {
2878 st->cr();
2879 print_on_extended(st);
2880 }
2881 }
2883 void G1CollectedHeap::print_on_extended(outputStream* st) const {
2884 PrintRegionClosure blk(st);
2885 _hrs->iterate(&blk);
2886 }
2888 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2889 if (G1CollectedHeap::use_parallel_gc_threads()) {
2890 workers()->print_worker_threads_on(st);
2891 }
2892 _cmThread->print_on(st);
2893 st->cr();
2894 _cm->print_worker_threads_on(st);
2895 _cg1r->print_worker_threads_on(st);
2896 st->cr();
2897 }
2899 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2900 if (G1CollectedHeap::use_parallel_gc_threads()) {
2901 workers()->threads_do(tc);
2902 }
2903 tc->do_thread(_cmThread);
2904 _cg1r->threads_do(tc);
2905 }
2907 void G1CollectedHeap::print_tracing_info() const {
2908 // We'll overload this to mean "trace GC pause statistics."
2909 if (TraceGen0Time || TraceGen1Time) {
2910 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
2911 // to that.
2912 g1_policy()->print_tracing_info();
2913 }
2914 if (G1SummarizeRSetStats) {
2915 g1_rem_set()->print_summary_info();
2916 }
2917 if (G1SummarizeConcMark) {
2918 concurrent_mark()->print_summary_info();
2919 }
2920 g1_policy()->print_yg_surv_rate_info();
2921 SpecializationStats::print();
2922 }
2924 int G1CollectedHeap::addr_to_arena_id(void* addr) const {
2925 HeapRegion* hr = heap_region_containing(addr);
2926 if (hr == NULL) {
2927 return 0;
2928 } else {
2929 return 1;
2930 }
2931 }
2933 G1CollectedHeap* G1CollectedHeap::heap() {
2934 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
2935 "not a garbage-first heap");
2936 return _g1h;
2937 }
2939 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2940 // always_do_update_barrier = false;
2941 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2942 // Call allocation profiler
2943 AllocationProfiler::iterate_since_last_gc();
2944 // Fill TLAB's and such
2945 ensure_parsability(true);
2946 }
2948 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
2949 // FIXME: what is this about?
2950 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2951 // is set.
2952 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
2953 "derived pointer present"));
2954 // always_do_update_barrier = true;
2955 }
2957 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2958 unsigned int gc_count_before,
2959 bool* succeeded) {
2960 assert_heap_not_locked_and_not_at_safepoint();
2961 g1_policy()->record_stop_world_start();
2962 VM_G1IncCollectionPause op(gc_count_before,
2963 word_size,
2964 false, /* should_initiate_conc_mark */
2965 g1_policy()->max_pause_time_ms(),
2966 GCCause::_g1_inc_collection_pause);
2967 VMThread::execute(&op);
2969 HeapWord* result = op.result();
2970 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2971 assert(result == NULL || ret_succeeded,
2972 "the result should be NULL if the VM did not succeed");
2973 *succeeded = ret_succeeded;
2975 assert_heap_not_locked();
2976 return result;
2977 }
2979 void
2980 G1CollectedHeap::doConcurrentMark() {
2981 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2982 if (!_cmThread->in_progress()) {
2983 _cmThread->set_started();
2984 CGC_lock->notify();
2985 }
2986 }
2988 class VerifyMarkedObjsClosure: public ObjectClosure {
2989 G1CollectedHeap* _g1h;
2990 public:
2991 VerifyMarkedObjsClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
2992 void do_object(oop obj) {
2993 assert(obj->mark()->is_marked() ? !_g1h->is_obj_dead(obj) : true,
2994 "markandsweep mark should agree with concurrent deadness");
2995 }
2996 };
2998 void
2999 G1CollectedHeap::checkConcurrentMark() {
3000 VerifyMarkedObjsClosure verifycl(this);
3001 // MutexLockerEx x(getMarkBitMapLock(),
3002 // Mutex::_no_safepoint_check_flag);
3003 object_iterate(&verifycl, false);
3004 }
3006 void G1CollectedHeap::do_sync_mark() {
3007 _cm->checkpointRootsInitial();
3008 _cm->markFromRoots();
3009 _cm->checkpointRootsFinal(false);
3010 }
3012 // <NEW PREDICTION>
3014 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
3015 bool young) {
3016 return _g1_policy->predict_region_elapsed_time_ms(hr, young);
3017 }
3019 void G1CollectedHeap::check_if_region_is_too_expensive(double
3020 predicted_time_ms) {
3021 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
3022 }
3024 size_t G1CollectedHeap::pending_card_num() {
3025 size_t extra_cards = 0;
3026 JavaThread *curr = Threads::first();
3027 while (curr != NULL) {
3028 DirtyCardQueue& dcq = curr->dirty_card_queue();
3029 extra_cards += dcq.size();
3030 curr = curr->next();
3031 }
3032 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3033 size_t buffer_size = dcqs.buffer_size();
3034 size_t buffer_num = dcqs.completed_buffers_num();
3035 return buffer_size * buffer_num + extra_cards;
3036 }
3038 size_t G1CollectedHeap::max_pending_card_num() {
3039 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3040 size_t buffer_size = dcqs.buffer_size();
3041 size_t buffer_num = dcqs.completed_buffers_num();
3042 int thread_num = Threads::number_of_threads();
3043 return (buffer_num + thread_num) * buffer_size;
3044 }
3046 size_t G1CollectedHeap::cards_scanned() {
3047 return g1_rem_set()->cardsScanned();
3048 }
3050 void
3051 G1CollectedHeap::setup_surviving_young_words() {
3052 guarantee( _surviving_young_words == NULL, "pre-condition" );
3053 size_t array_length = g1_policy()->young_cset_length();
3054 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
3055 if (_surviving_young_words == NULL) {
3056 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3057 "Not enough space for young surv words summary.");
3058 }
3059 memset(_surviving_young_words, 0, array_length * sizeof(size_t));
3060 #ifdef ASSERT
3061 for (size_t i = 0; i < array_length; ++i) {
3062 assert( _surviving_young_words[i] == 0, "memset above" );
3063 }
3064 #endif // !ASSERT
3065 }
3067 void
3068 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3069 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3070 size_t array_length = g1_policy()->young_cset_length();
3071 for (size_t i = 0; i < array_length; ++i)
3072 _surviving_young_words[i] += surv_young_words[i];
3073 }
3075 void
3076 G1CollectedHeap::cleanup_surviving_young_words() {
3077 guarantee( _surviving_young_words != NULL, "pre-condition" );
3078 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3079 _surviving_young_words = NULL;
3080 }
3082 // </NEW PREDICTION>
3084 struct PrepareForRSScanningClosure : public HeapRegionClosure {
3085 bool doHeapRegion(HeapRegion *r) {
3086 r->rem_set()->set_iter_claimed(0);
3087 return false;
3088 }
3089 };
3091 #if TASKQUEUE_STATS
3092 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3093 st->print_raw_cr("GC Task Stats");
3094 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3095 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3096 }
3098 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3099 print_taskqueue_stats_hdr(st);
3101 TaskQueueStats totals;
3102 const int n = workers() != NULL ? workers()->total_workers() : 1;
3103 for (int i = 0; i < n; ++i) {
3104 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3105 totals += task_queue(i)->stats;
3106 }
3107 st->print_raw("tot "); totals.print(st); st->cr();
3109 DEBUG_ONLY(totals.verify());
3110 }
3112 void G1CollectedHeap::reset_taskqueue_stats() {
3113 const int n = workers() != NULL ? workers()->total_workers() : 1;
3114 for (int i = 0; i < n; ++i) {
3115 task_queue(i)->stats.reset();
3116 }
3117 }
3118 #endif // TASKQUEUE_STATS
3120 bool
3121 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3122 assert_at_safepoint(true /* should_be_vm_thread */);
3123 guarantee(!is_gc_active(), "collection is not reentrant");
3125 if (GC_locker::check_active_before_gc()) {
3126 return false;
3127 }
3129 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3130 ResourceMark rm;
3132 if (PrintHeapAtGC) {
3133 Universe::print_heap_before_gc();
3134 }
3136 verify_region_sets_optional();
3137 verify_dirty_young_regions();
3139 {
3140 // This call will decide whether this pause is an initial-mark
3141 // pause. If it is, during_initial_mark_pause() will return true
3142 // for the duration of this pause.
3143 g1_policy()->decide_on_conc_mark_initiation();
3145 char verbose_str[128];
3146 sprintf(verbose_str, "GC pause ");
3147 if (g1_policy()->in_young_gc_mode()) {
3148 if (g1_policy()->full_young_gcs())
3149 strcat(verbose_str, "(young)");
3150 else
3151 strcat(verbose_str, "(partial)");
3152 }
3153 if (g1_policy()->during_initial_mark_pause()) {
3154 strcat(verbose_str, " (initial-mark)");
3155 // We are about to start a marking cycle, so we increment the
3156 // full collection counter.
3157 increment_total_full_collections();
3158 }
3160 // if PrintGCDetails is on, we'll print long statistics information
3161 // in the collector policy code, so let's not print this as the output
3162 // is messy if we do.
3163 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
3164 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
3165 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
3167 TraceMemoryManagerStats tms(false /* fullGC */);
3169 // If the secondary_free_list is not empty, append it to the
3170 // free_list. No need to wait for the cleanup operation to finish;
3171 // the region allocation code will check the secondary_free_list
3172 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3173 // set, skip this step so that the region allocation code has to
3174 // get entries from the secondary_free_list.
3175 if (!G1StressConcRegionFreeing) {
3176 append_secondary_free_list_if_not_empty_with_lock();
3177 }
3179 increment_gc_time_stamp();
3181 if (g1_policy()->in_young_gc_mode()) {
3182 assert(check_young_list_well_formed(),
3183 "young list should be well formed");
3184 }
3186 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3187 IsGCActiveMark x;
3189 gc_prologue(false);
3190 increment_total_collections(false /* full gc */);
3192 #if G1_REM_SET_LOGGING
3193 gclog_or_tty->print_cr("\nJust chose CS, heap:");
3194 print();
3195 #endif
3197 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3198 HandleMark hm; // Discard invalid handles created during verification
3199 gclog_or_tty->print(" VerifyBeforeGC:");
3200 prepare_for_verify();
3201 Universe::verify(false);
3202 }
3204 COMPILER2_PRESENT(DerivedPointerTable::clear());
3206 // Please see comment in G1CollectedHeap::ref_processing_init()
3207 // to see how reference processing currently works in G1.
3208 //
3209 // We want to turn off ref discovery, if necessary, and turn it back on
3210 // on again later if we do. XXX Dubious: why is discovery disabled?
3211 bool was_enabled = ref_processor()->discovery_enabled();
3212 if (was_enabled) ref_processor()->disable_discovery();
3214 // Forget the current alloc region (we might even choose it to be part
3215 // of the collection set!).
3216 release_mutator_alloc_region();
3218 // The elapsed time induced by the start time below deliberately elides
3219 // the possible verification above.
3220 double start_time_sec = os::elapsedTime();
3221 size_t start_used_bytes = used();
3223 #if YOUNG_LIST_VERBOSE
3224 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3225 _young_list->print();
3226 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3227 #endif // YOUNG_LIST_VERBOSE
3229 g1_policy()->record_collection_pause_start(start_time_sec,
3230 start_used_bytes);
3232 #if YOUNG_LIST_VERBOSE
3233 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3234 _young_list->print();
3235 #endif // YOUNG_LIST_VERBOSE
3237 if (g1_policy()->during_initial_mark_pause()) {
3238 concurrent_mark()->checkpointRootsInitialPre();
3239 }
3240 save_marks();
3242 // We must do this before any possible evacuation that should propagate
3243 // marks.
3244 if (mark_in_progress()) {
3245 double start_time_sec = os::elapsedTime();
3247 _cm->drainAllSATBBuffers();
3248 double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0;
3249 g1_policy()->record_satb_drain_time(finish_mark_ms);
3250 }
3251 // Record the number of elements currently on the mark stack, so we
3252 // only iterate over these. (Since evacuation may add to the mark
3253 // stack, doing more exposes race conditions.) If no mark is in
3254 // progress, this will be zero.
3255 _cm->set_oops_do_bound();
3257 if (mark_in_progress())
3258 concurrent_mark()->newCSet();
3260 #if YOUNG_LIST_VERBOSE
3261 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3262 _young_list->print();
3263 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3264 #endif // YOUNG_LIST_VERBOSE
3266 g1_policy()->choose_collection_set(target_pause_time_ms);
3268 // Nothing to do if we were unable to choose a collection set.
3269 #if G1_REM_SET_LOGGING
3270 gclog_or_tty->print_cr("\nAfter pause, heap:");
3271 print();
3272 #endif
3273 PrepareForRSScanningClosure prepare_for_rs_scan;
3274 collection_set_iterate(&prepare_for_rs_scan);
3276 setup_surviving_young_words();
3278 // Set up the gc allocation regions.
3279 get_gc_alloc_regions();
3281 // Actually do the work...
3282 evacuate_collection_set();
3284 free_collection_set(g1_policy()->collection_set());
3285 g1_policy()->clear_collection_set();
3287 cleanup_surviving_young_words();
3289 // Start a new incremental collection set for the next pause.
3290 g1_policy()->start_incremental_cset_building();
3292 // Clear the _cset_fast_test bitmap in anticipation of adding
3293 // regions to the incremental collection set for the next
3294 // evacuation pause.
3295 clear_cset_fast_test();
3297 if (g1_policy()->in_young_gc_mode()) {
3298 _young_list->reset_sampled_info();
3300 // Don't check the whole heap at this point as the
3301 // GC alloc regions from this pause have been tagged
3302 // as survivors and moved on to the survivor list.
3303 // Survivor regions will fail the !is_young() check.
3304 assert(check_young_list_empty(false /* check_heap */),
3305 "young list should be empty");
3307 #if YOUNG_LIST_VERBOSE
3308 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3309 _young_list->print();
3310 #endif // YOUNG_LIST_VERBOSE
3312 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3313 _young_list->first_survivor_region(),
3314 _young_list->last_survivor_region());
3316 _young_list->reset_auxilary_lists();
3317 }
3319 if (evacuation_failed()) {
3320 _summary_bytes_used = recalculate_used();
3321 } else {
3322 // The "used" of the the collection set have already been subtracted
3323 // when they were freed. Add in the bytes evacuated.
3324 _summary_bytes_used += g1_policy()->bytes_in_to_space();
3325 }
3327 if (g1_policy()->in_young_gc_mode() &&
3328 g1_policy()->during_initial_mark_pause()) {
3329 concurrent_mark()->checkpointRootsInitialPost();
3330 set_marking_started();
3331 // CAUTION: after the doConcurrentMark() call below,
3332 // the concurrent marking thread(s) could be running
3333 // concurrently with us. Make sure that anything after
3334 // this point does not assume that we are the only GC thread
3335 // running. Note: of course, the actual marking work will
3336 // not start until the safepoint itself is released in
3337 // ConcurrentGCThread::safepoint_desynchronize().
3338 doConcurrentMark();
3339 }
3341 #if YOUNG_LIST_VERBOSE
3342 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3343 _young_list->print();
3344 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3345 #endif // YOUNG_LIST_VERBOSE
3347 init_mutator_alloc_region();
3349 double end_time_sec = os::elapsedTime();
3350 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3351 g1_policy()->record_pause_time_ms(pause_time_ms);
3352 g1_policy()->record_collection_pause_end();
3354 MemoryService::track_memory_usage();
3356 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3357 HandleMark hm; // Discard invalid handles created during verification
3358 gclog_or_tty->print(" VerifyAfterGC:");
3359 prepare_for_verify();
3360 Universe::verify(false);
3361 }
3363 if (was_enabled) ref_processor()->enable_discovery();
3365 {
3366 size_t expand_bytes = g1_policy()->expansion_amount();
3367 if (expand_bytes > 0) {
3368 size_t bytes_before = capacity();
3369 if (!expand(expand_bytes)) {
3370 // We failed to expand the heap so let's verify that
3371 // committed/uncommitted amount match the backing store
3372 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3373 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3374 }
3375 }
3376 }
3378 if (mark_in_progress()) {
3379 concurrent_mark()->update_g1_committed();
3380 }
3382 #ifdef TRACESPINNING
3383 ParallelTaskTerminator::print_termination_counts();
3384 #endif
3386 gc_epilogue(false);
3387 }
3389 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3390 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3391 print_tracing_info();
3392 vm_exit(-1);
3393 }
3394 }
3396 verify_region_sets_optional();
3398 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3399 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3401 if (PrintHeapAtGC) {
3402 Universe::print_heap_after_gc();
3403 }
3404 if (G1SummarizeRSetStats &&
3405 (G1SummarizeRSetStatsPeriod > 0) &&
3406 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3407 g1_rem_set()->print_summary_info();
3408 }
3410 return true;
3411 }
3413 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3414 {
3415 size_t gclab_word_size;
3416 switch (purpose) {
3417 case GCAllocForSurvived:
3418 gclab_word_size = YoungPLABSize;
3419 break;
3420 case GCAllocForTenured:
3421 gclab_word_size = OldPLABSize;
3422 break;
3423 default:
3424 assert(false, "unknown GCAllocPurpose");
3425 gclab_word_size = OldPLABSize;
3426 break;
3427 }
3428 return gclab_word_size;
3429 }
3431 void G1CollectedHeap::init_mutator_alloc_region() {
3432 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
3433 _mutator_alloc_region.init();
3434 }
3436 void G1CollectedHeap::release_mutator_alloc_region() {
3437 _mutator_alloc_region.release();
3438 assert(_mutator_alloc_region.get() == NULL, "post-condition");
3439 }
3441 void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {
3442 assert(purpose >= 0 && purpose < GCAllocPurposeCount, "invalid purpose");
3443 // make sure we don't call set_gc_alloc_region() multiple times on
3444 // the same region
3445 assert(r == NULL || !r->is_gc_alloc_region(),
3446 "shouldn't already be a GC alloc region");
3447 assert(r == NULL || !r->isHumongous(),
3448 "humongous regions shouldn't be used as GC alloc regions");
3450 HeapWord* original_top = NULL;
3451 if (r != NULL)
3452 original_top = r->top();
3454 // We will want to record the used space in r as being there before gc.
3455 // One we install it as a GC alloc region it's eligible for allocation.
3456 // So record it now and use it later.
3457 size_t r_used = 0;
3458 if (r != NULL) {
3459 r_used = r->used();
3461 if (G1CollectedHeap::use_parallel_gc_threads()) {
3462 // need to take the lock to guard against two threads calling
3463 // get_gc_alloc_region concurrently (very unlikely but...)
3464 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3465 r->save_marks();
3466 }
3467 }
3468 HeapRegion* old_alloc_region = _gc_alloc_regions[purpose];
3469 _gc_alloc_regions[purpose] = r;
3470 if (old_alloc_region != NULL) {
3471 // Replace aliases too.
3472 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3473 if (_gc_alloc_regions[ap] == old_alloc_region) {
3474 _gc_alloc_regions[ap] = r;
3475 }
3476 }
3477 }
3478 if (r != NULL) {
3479 push_gc_alloc_region(r);
3480 if (mark_in_progress() && original_top != r->next_top_at_mark_start()) {
3481 // We are using a region as a GC alloc region after it has been used
3482 // as a mutator allocation region during the current marking cycle.
3483 // The mutator-allocated objects are currently implicitly marked, but
3484 // when we move hr->next_top_at_mark_start() forward at the the end
3485 // of the GC pause, they won't be. We therefore mark all objects in
3486 // the "gap". We do this object-by-object, since marking densely
3487 // does not currently work right with marking bitmap iteration. This
3488 // means we rely on TLAB filling at the start of pauses, and no
3489 // "resuscitation" of filled TLAB's. If we want to do this, we need
3490 // to fix the marking bitmap iteration.
3491 HeapWord* curhw = r->next_top_at_mark_start();
3492 HeapWord* t = original_top;
3494 while (curhw < t) {
3495 oop cur = (oop)curhw;
3496 // We'll assume parallel for generality. This is rare code.
3497 concurrent_mark()->markAndGrayObjectIfNecessary(cur); // can't we just mark them?
3498 curhw = curhw + cur->size();
3499 }
3500 assert(curhw == t, "Should have parsed correctly.");
3501 }
3502 if (G1PolicyVerbose > 1) {
3503 gclog_or_tty->print("New alloc region ["PTR_FORMAT", "PTR_FORMAT", " PTR_FORMAT") "
3504 "for survivors:", r->bottom(), original_top, r->end());
3505 r->print();
3506 }
3507 g1_policy()->record_before_bytes(r_used);
3508 }
3509 }
3511 void G1CollectedHeap::push_gc_alloc_region(HeapRegion* hr) {
3512 assert(Thread::current()->is_VM_thread() ||
3513 FreeList_lock->owned_by_self(), "Precondition");
3514 assert(!hr->is_gc_alloc_region() && !hr->in_collection_set(),
3515 "Precondition.");
3516 hr->set_is_gc_alloc_region(true);
3517 hr->set_next_gc_alloc_region(_gc_alloc_region_list);
3518 _gc_alloc_region_list = hr;
3519 }
3521 #ifdef G1_DEBUG
3522 class FindGCAllocRegion: public HeapRegionClosure {
3523 public:
3524 bool doHeapRegion(HeapRegion* r) {
3525 if (r->is_gc_alloc_region()) {
3526 gclog_or_tty->print_cr("Region %d ["PTR_FORMAT"...] is still a gc_alloc_region.",
3527 r->hrs_index(), r->bottom());
3528 }
3529 return false;
3530 }
3531 };
3532 #endif // G1_DEBUG
3534 void G1CollectedHeap::forget_alloc_region_list() {
3535 assert_at_safepoint(true /* should_be_vm_thread */);
3536 while (_gc_alloc_region_list != NULL) {
3537 HeapRegion* r = _gc_alloc_region_list;
3538 assert(r->is_gc_alloc_region(), "Invariant.");
3539 // We need HeapRegion::oops_on_card_seq_iterate_careful() to work on
3540 // newly allocated data in order to be able to apply deferred updates
3541 // before the GC is done for verification purposes (i.e to allow
3542 // G1HRRSFlushLogBuffersOnVerify). It's safe thing to do after the
3543 // collection.
3544 r->ContiguousSpace::set_saved_mark();
3545 _gc_alloc_region_list = r->next_gc_alloc_region();
3546 r->set_next_gc_alloc_region(NULL);
3547 r->set_is_gc_alloc_region(false);
3548 if (r->is_survivor()) {
3549 if (r->is_empty()) {
3550 r->set_not_young();
3551 } else {
3552 _young_list->add_survivor_region(r);
3553 }
3554 }
3555 }
3556 #ifdef G1_DEBUG
3557 FindGCAllocRegion fa;
3558 heap_region_iterate(&fa);
3559 #endif // G1_DEBUG
3560 }
3563 bool G1CollectedHeap::check_gc_alloc_regions() {
3564 // TODO: allocation regions check
3565 return true;
3566 }
3568 void G1CollectedHeap::get_gc_alloc_regions() {
3569 // First, let's check that the GC alloc region list is empty (it should)
3570 assert(_gc_alloc_region_list == NULL, "invariant");
3572 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3573 assert(_gc_alloc_regions[ap] == NULL, "invariant");
3574 assert(_gc_alloc_region_counts[ap] == 0, "invariant");
3576 // Create new GC alloc regions.
3577 HeapRegion* alloc_region = _retained_gc_alloc_regions[ap];
3578 _retained_gc_alloc_regions[ap] = NULL;
3580 if (alloc_region != NULL) {
3581 assert(_retain_gc_alloc_region[ap], "only way to retain a GC region");
3583 // let's make sure that the GC alloc region is not tagged as such
3584 // outside a GC operation
3585 assert(!alloc_region->is_gc_alloc_region(), "sanity");
3587 if (alloc_region->in_collection_set() ||
3588 alloc_region->top() == alloc_region->end() ||
3589 alloc_region->top() == alloc_region->bottom() ||
3590 alloc_region->isHumongous()) {
3591 // we will discard the current GC alloc region if
3592 // * it's in the collection set (it can happen!),
3593 // * it's already full (no point in using it),
3594 // * it's empty (this means that it was emptied during
3595 // a cleanup and it should be on the free list now), or
3596 // * it's humongous (this means that it was emptied
3597 // during a cleanup and was added to the free list, but
3598 // has been subseqently used to allocate a humongous
3599 // object that may be less than the region size).
3601 alloc_region = NULL;
3602 }
3603 }
3605 if (alloc_region == NULL) {
3606 // we will get a new GC alloc region
3607 alloc_region = new_gc_alloc_region(ap, HeapRegion::GrainWords);
3608 } else {
3609 // the region was retained from the last collection
3610 ++_gc_alloc_region_counts[ap];
3611 if (G1PrintHeapRegions) {
3612 gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT", "PTR_FORMAT"], "
3613 "top "PTR_FORMAT,
3614 alloc_region->hrs_index(), alloc_region->bottom(), alloc_region->end(), alloc_region->top());
3615 }
3616 }
3618 if (alloc_region != NULL) {
3619 assert(_gc_alloc_regions[ap] == NULL, "pre-condition");
3620 set_gc_alloc_region(ap, alloc_region);
3621 }
3623 assert(_gc_alloc_regions[ap] == NULL ||
3624 _gc_alloc_regions[ap]->is_gc_alloc_region(),
3625 "the GC alloc region should be tagged as such");
3626 assert(_gc_alloc_regions[ap] == NULL ||
3627 _gc_alloc_regions[ap] == _gc_alloc_region_list,
3628 "the GC alloc region should be the same as the GC alloc list head");
3629 }
3630 // Set alternative regions for allocation purposes that have reached
3631 // their limit.
3632 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3633 GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(ap);
3634 if (_gc_alloc_regions[ap] == NULL && alt_purpose != ap) {
3635 _gc_alloc_regions[ap] = _gc_alloc_regions[alt_purpose];
3636 }
3637 }
3638 assert(check_gc_alloc_regions(), "alloc regions messed up");
3639 }
3641 void G1CollectedHeap::release_gc_alloc_regions(bool totally) {
3642 // We keep a separate list of all regions that have been alloc regions in
3643 // the current collection pause. Forget that now. This method will
3644 // untag the GC alloc regions and tear down the GC alloc region
3645 // list. It's desirable that no regions are tagged as GC alloc
3646 // outside GCs.
3648 forget_alloc_region_list();
3650 // The current alloc regions contain objs that have survived
3651 // collection. Make them no longer GC alloc regions.
3652 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3653 HeapRegion* r = _gc_alloc_regions[ap];
3654 _retained_gc_alloc_regions[ap] = NULL;
3655 _gc_alloc_region_counts[ap] = 0;
3657 if (r != NULL) {
3658 // we retain nothing on _gc_alloc_regions between GCs
3659 set_gc_alloc_region(ap, NULL);
3661 if (r->is_empty()) {
3662 // We didn't actually allocate anything in it; let's just put
3663 // it back on the free list.
3664 _free_list.add_as_head(r);
3665 } else if (_retain_gc_alloc_region[ap] && !totally) {
3666 // retain it so that we can use it at the beginning of the next GC
3667 _retained_gc_alloc_regions[ap] = r;
3668 }
3669 }
3670 }
3671 }
3673 #ifndef PRODUCT
3674 // Useful for debugging
3676 void G1CollectedHeap::print_gc_alloc_regions() {
3677 gclog_or_tty->print_cr("GC alloc regions");
3678 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3679 HeapRegion* r = _gc_alloc_regions[ap];
3680 if (r == NULL) {
3681 gclog_or_tty->print_cr(" %2d : "PTR_FORMAT, ap, NULL);
3682 } else {
3683 gclog_or_tty->print_cr(" %2d : "PTR_FORMAT" "SIZE_FORMAT,
3684 ap, r->bottom(), r->used());
3685 }
3686 }
3687 }
3688 #endif // PRODUCT
3690 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
3691 _drain_in_progress = false;
3692 set_evac_failure_closure(cl);
3693 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
3694 }
3696 void G1CollectedHeap::finalize_for_evac_failure() {
3697 assert(_evac_failure_scan_stack != NULL &&
3698 _evac_failure_scan_stack->length() == 0,
3699 "Postcondition");
3700 assert(!_drain_in_progress, "Postcondition");
3701 delete _evac_failure_scan_stack;
3702 _evac_failure_scan_stack = NULL;
3703 }
3707 // *** Sequential G1 Evacuation
3709 class G1IsAliveClosure: public BoolObjectClosure {
3710 G1CollectedHeap* _g1;
3711 public:
3712 G1IsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3713 void do_object(oop p) { assert(false, "Do not call."); }
3714 bool do_object_b(oop p) {
3715 // It is reachable if it is outside the collection set, or is inside
3716 // and forwarded.
3718 #ifdef G1_DEBUG
3719 gclog_or_tty->print_cr("is alive "PTR_FORMAT" in CS %d forwarded %d overall %d",
3720 (void*) p, _g1->obj_in_cs(p), p->is_forwarded(),
3721 !_g1->obj_in_cs(p) || p->is_forwarded());
3722 #endif // G1_DEBUG
3724 return !_g1->obj_in_cs(p) || p->is_forwarded();
3725 }
3726 };
3728 class G1KeepAliveClosure: public OopClosure {
3729 G1CollectedHeap* _g1;
3730 public:
3731 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3732 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3733 void do_oop( oop* p) {
3734 oop obj = *p;
3735 #ifdef G1_DEBUG
3736 if (PrintGC && Verbose) {
3737 gclog_or_tty->print_cr("keep alive *"PTR_FORMAT" = "PTR_FORMAT" "PTR_FORMAT,
3738 p, (void*) obj, (void*) *p);
3739 }
3740 #endif // G1_DEBUG
3742 if (_g1->obj_in_cs(obj)) {
3743 assert( obj->is_forwarded(), "invariant" );
3744 *p = obj->forwardee();
3745 #ifdef G1_DEBUG
3746 gclog_or_tty->print_cr(" in CSet: moved "PTR_FORMAT" -> "PTR_FORMAT,
3747 (void*) obj, (void*) *p);
3748 #endif // G1_DEBUG
3749 }
3750 }
3751 };
3753 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
3754 private:
3755 G1CollectedHeap* _g1;
3756 DirtyCardQueue *_dcq;
3757 CardTableModRefBS* _ct_bs;
3759 public:
3760 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
3761 _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
3763 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3764 virtual void do_oop( oop* p) { do_oop_work(p); }
3765 template <class T> void do_oop_work(T* p) {
3766 assert(_from->is_in_reserved(p), "paranoia");
3767 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
3768 !_from->is_survivor()) {
3769 size_t card_index = _ct_bs->index_for(p);
3770 if (_ct_bs->mark_card_deferred(card_index)) {
3771 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
3772 }
3773 }
3774 }
3775 };
3777 class RemoveSelfPointerClosure: public ObjectClosure {
3778 private:
3779 G1CollectedHeap* _g1;
3780 ConcurrentMark* _cm;
3781 HeapRegion* _hr;
3782 size_t _prev_marked_bytes;
3783 size_t _next_marked_bytes;
3784 OopsInHeapRegionClosure *_cl;
3785 public:
3786 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr,
3787 OopsInHeapRegionClosure* cl) :
3788 _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0),
3789 _next_marked_bytes(0), _cl(cl) {}
3791 size_t prev_marked_bytes() { return _prev_marked_bytes; }
3792 size_t next_marked_bytes() { return _next_marked_bytes; }
3794 // <original comment>
3795 // The original idea here was to coalesce evacuated and dead objects.
3796 // However that caused complications with the block offset table (BOT).
3797 // In particular if there were two TLABs, one of them partially refined.
3798 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
3799 // The BOT entries of the unrefined part of TLAB_2 point to the start
3800 // of TLAB_2. If the last object of the TLAB_1 and the first object
3801 // of TLAB_2 are coalesced, then the cards of the unrefined part
3802 // would point into middle of the filler object.
3803 // The current approach is to not coalesce and leave the BOT contents intact.
3804 // </original comment>
3805 //
3806 // We now reset the BOT when we start the object iteration over the
3807 // region and refine its entries for every object we come across. So
3808 // the above comment is not really relevant and we should be able
3809 // to coalesce dead objects if we want to.
3810 void do_object(oop obj) {
3811 HeapWord* obj_addr = (HeapWord*) obj;
3812 assert(_hr->is_in(obj_addr), "sanity");
3813 size_t obj_size = obj->size();
3814 _hr->update_bot_for_object(obj_addr, obj_size);
3815 if (obj->is_forwarded() && obj->forwardee() == obj) {
3816 // The object failed to move.
3817 assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
3818 _cm->markPrev(obj);
3819 assert(_cm->isPrevMarked(obj), "Should be marked!");
3820 _prev_marked_bytes += (obj_size * HeapWordSize);
3821 if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
3822 _cm->markAndGrayObjectIfNecessary(obj);
3823 }
3824 obj->set_mark(markOopDesc::prototype());
3825 // While we were processing RSet buffers during the
3826 // collection, we actually didn't scan any cards on the
3827 // collection set, since we didn't want to update remebered
3828 // sets with entries that point into the collection set, given
3829 // that live objects fromthe collection set are about to move
3830 // and such entries will be stale very soon. This change also
3831 // dealt with a reliability issue which involved scanning a
3832 // card in the collection set and coming across an array that
3833 // was being chunked and looking malformed. The problem is
3834 // that, if evacuation fails, we might have remembered set
3835 // entries missing given that we skipped cards on the
3836 // collection set. So, we'll recreate such entries now.
3837 obj->oop_iterate(_cl);
3838 assert(_cm->isPrevMarked(obj), "Should be marked!");
3839 } else {
3840 // The object has been either evacuated or is dead. Fill it with a
3841 // dummy object.
3842 MemRegion mr((HeapWord*)obj, obj_size);
3843 CollectedHeap::fill_with_object(mr);
3844 _cm->clearRangeBothMaps(mr);
3845 }
3846 }
3847 };
3849 void G1CollectedHeap::remove_self_forwarding_pointers() {
3850 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
3851 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
3852 UpdateRSetDeferred deferred_update(_g1h, &dcq);
3853 OopsInHeapRegionClosure *cl;
3854 if (G1DeferredRSUpdate) {
3855 cl = &deferred_update;
3856 } else {
3857 cl = &immediate_update;
3858 }
3859 HeapRegion* cur = g1_policy()->collection_set();
3860 while (cur != NULL) {
3861 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
3862 assert(!cur->isHumongous(), "sanity");
3864 if (cur->evacuation_failed()) {
3865 assert(cur->in_collection_set(), "bad CS");
3866 RemoveSelfPointerClosure rspc(_g1h, cur, cl);
3868 cur->reset_bot();
3869 cl->set_region(cur);
3870 cur->object_iterate(&rspc);
3872 // A number of manipulations to make the TAMS be the current top,
3873 // and the marked bytes be the ones observed in the iteration.
3874 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
3875 // The comments below are the postconditions achieved by the
3876 // calls. Note especially the last such condition, which says that
3877 // the count of marked bytes has been properly restored.
3878 cur->note_start_of_marking(false);
3879 // _next_top_at_mark_start == top, _next_marked_bytes == 0
3880 cur->add_to_marked_bytes(rspc.prev_marked_bytes());
3881 // _next_marked_bytes == prev_marked_bytes.
3882 cur->note_end_of_marking();
3883 // _prev_top_at_mark_start == top(),
3884 // _prev_marked_bytes == prev_marked_bytes
3885 }
3886 // If there is no mark in progress, we modified the _next variables
3887 // above needlessly, but harmlessly.
3888 if (_g1h->mark_in_progress()) {
3889 cur->note_start_of_marking(false);
3890 // _next_top_at_mark_start == top, _next_marked_bytes == 0
3891 // _next_marked_bytes == next_marked_bytes.
3892 }
3894 // Now make sure the region has the right index in the sorted array.
3895 g1_policy()->note_change_in_marked_bytes(cur);
3896 }
3897 cur = cur->next_in_collection_set();
3898 }
3899 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
3901 // Now restore saved marks, if any.
3902 if (_objs_with_preserved_marks != NULL) {
3903 assert(_preserved_marks_of_objs != NULL, "Both or none.");
3904 guarantee(_objs_with_preserved_marks->length() ==
3905 _preserved_marks_of_objs->length(), "Both or none.");
3906 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
3907 oop obj = _objs_with_preserved_marks->at(i);
3908 markOop m = _preserved_marks_of_objs->at(i);
3909 obj->set_mark(m);
3910 }
3911 // Delete the preserved marks growable arrays (allocated on the C heap).
3912 delete _objs_with_preserved_marks;
3913 delete _preserved_marks_of_objs;
3914 _objs_with_preserved_marks = NULL;
3915 _preserved_marks_of_objs = NULL;
3916 }
3917 }
3919 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
3920 _evac_failure_scan_stack->push(obj);
3921 }
3923 void G1CollectedHeap::drain_evac_failure_scan_stack() {
3924 assert(_evac_failure_scan_stack != NULL, "precondition");
3926 while (_evac_failure_scan_stack->length() > 0) {
3927 oop obj = _evac_failure_scan_stack->pop();
3928 _evac_failure_closure->set_region(heap_region_containing(obj));
3929 obj->oop_iterate_backwards(_evac_failure_closure);
3930 }
3931 }
3933 oop
3934 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
3935 oop old) {
3936 markOop m = old->mark();
3937 oop forward_ptr = old->forward_to_atomic(old);
3938 if (forward_ptr == NULL) {
3939 // Forward-to-self succeeded.
3940 if (_evac_failure_closure != cl) {
3941 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
3942 assert(!_drain_in_progress,
3943 "Should only be true while someone holds the lock.");
3944 // Set the global evac-failure closure to the current thread's.
3945 assert(_evac_failure_closure == NULL, "Or locking has failed.");
3946 set_evac_failure_closure(cl);
3947 // Now do the common part.
3948 handle_evacuation_failure_common(old, m);
3949 // Reset to NULL.
3950 set_evac_failure_closure(NULL);
3951 } else {
3952 // The lock is already held, and this is recursive.
3953 assert(_drain_in_progress, "This should only be the recursive case.");
3954 handle_evacuation_failure_common(old, m);
3955 }
3956 return old;
3957 } else {
3958 // Someone else had a place to copy it.
3959 return forward_ptr;
3960 }
3961 }
3963 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
3964 set_evacuation_failed(true);
3966 preserve_mark_if_necessary(old, m);
3968 HeapRegion* r = heap_region_containing(old);
3969 if (!r->evacuation_failed()) {
3970 r->set_evacuation_failed(true);
3971 if (G1PrintHeapRegions) {
3972 gclog_or_tty->print("overflow in heap region "PTR_FORMAT" "
3973 "["PTR_FORMAT","PTR_FORMAT")\n",
3974 r, r->bottom(), r->end());
3975 }
3976 }
3978 push_on_evac_failure_scan_stack(old);
3980 if (!_drain_in_progress) {
3981 // prevent recursion in copy_to_survivor_space()
3982 _drain_in_progress = true;
3983 drain_evac_failure_scan_stack();
3984 _drain_in_progress = false;
3985 }
3986 }
3988 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
3989 assert(evacuation_failed(), "Oversaving!");
3990 // We want to call the "for_promotion_failure" version only in the
3991 // case of a promotion failure.
3992 if (m->must_be_preserved_for_promotion_failure(obj)) {
3993 if (_objs_with_preserved_marks == NULL) {
3994 assert(_preserved_marks_of_objs == NULL, "Both or none.");
3995 _objs_with_preserved_marks =
3996 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
3997 _preserved_marks_of_objs =
3998 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
3999 }
4000 _objs_with_preserved_marks->push(obj);
4001 _preserved_marks_of_objs->push(m);
4002 }
4003 }
4005 // *** Parallel G1 Evacuation
4007 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4008 size_t word_size) {
4009 assert(!isHumongous(word_size),
4010 err_msg("we should not be seeing humongous allocation requests "
4011 "during GC, word_size = "SIZE_FORMAT, word_size));
4013 HeapRegion* alloc_region = _gc_alloc_regions[purpose];
4014 // let the caller handle alloc failure
4015 if (alloc_region == NULL) return NULL;
4017 HeapWord* block = alloc_region->par_allocate(word_size);
4018 if (block == NULL) {
4019 block = allocate_during_gc_slow(purpose, alloc_region, true, word_size);
4020 }
4021 return block;
4022 }
4024 void G1CollectedHeap::retire_alloc_region(HeapRegion* alloc_region,
4025 bool par) {
4026 // Another thread might have obtained alloc_region for the given
4027 // purpose, and might be attempting to allocate in it, and might
4028 // succeed. Therefore, we can't do the "finalization" stuff on the
4029 // region below until we're sure the last allocation has happened.
4030 // We ensure this by allocating the remaining space with a garbage
4031 // object.
4032 if (par) par_allocate_remaining_space(alloc_region);
4033 // Now we can do the post-GC stuff on the region.
4034 alloc_region->note_end_of_copying();
4035 g1_policy()->record_after_bytes(alloc_region->used());
4036 }
4038 HeapWord*
4039 G1CollectedHeap::allocate_during_gc_slow(GCAllocPurpose purpose,
4040 HeapRegion* alloc_region,
4041 bool par,
4042 size_t word_size) {
4043 assert(!isHumongous(word_size),
4044 err_msg("we should not be seeing humongous allocation requests "
4045 "during GC, word_size = "SIZE_FORMAT, word_size));
4047 // We need to make sure we serialize calls to this method. Given
4048 // that the FreeList_lock guards accesses to the free_list anyway,
4049 // and we need to potentially remove a region from it, we'll use it
4050 // to protect the whole call.
4051 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4053 HeapWord* block = NULL;
4054 // In the parallel case, a previous thread to obtain the lock may have
4055 // already assigned a new gc_alloc_region.
4056 if (alloc_region != _gc_alloc_regions[purpose]) {
4057 assert(par, "But should only happen in parallel case.");
4058 alloc_region = _gc_alloc_regions[purpose];
4059 if (alloc_region == NULL) return NULL;
4060 block = alloc_region->par_allocate(word_size);
4061 if (block != NULL) return block;
4062 // Otherwise, continue; this new region is empty, too.
4063 }
4064 assert(alloc_region != NULL, "We better have an allocation region");
4065 retire_alloc_region(alloc_region, par);
4067 if (_gc_alloc_region_counts[purpose] >= g1_policy()->max_regions(purpose)) {
4068 // Cannot allocate more regions for the given purpose.
4069 GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(purpose);
4070 // Is there an alternative?
4071 if (purpose != alt_purpose) {
4072 HeapRegion* alt_region = _gc_alloc_regions[alt_purpose];
4073 // Has not the alternative region been aliased?
4074 if (alloc_region != alt_region && alt_region != NULL) {
4075 // Try to allocate in the alternative region.
4076 if (par) {
4077 block = alt_region->par_allocate(word_size);
4078 } else {
4079 block = alt_region->allocate(word_size);
4080 }
4081 // Make an alias.
4082 _gc_alloc_regions[purpose] = _gc_alloc_regions[alt_purpose];
4083 if (block != NULL) {
4084 return block;
4085 }
4086 retire_alloc_region(alt_region, par);
4087 }
4088 // Both the allocation region and the alternative one are full
4089 // and aliased, replace them with a new allocation region.
4090 purpose = alt_purpose;
4091 } else {
4092 set_gc_alloc_region(purpose, NULL);
4093 return NULL;
4094 }
4095 }
4097 // Now allocate a new region for allocation.
4098 alloc_region = new_gc_alloc_region(purpose, word_size);
4100 // let the caller handle alloc failure
4101 if (alloc_region != NULL) {
4103 assert(check_gc_alloc_regions(), "alloc regions messed up");
4104 assert(alloc_region->saved_mark_at_top(),
4105 "Mark should have been saved already.");
4106 // This must be done last: once it's installed, other regions may
4107 // allocate in it (without holding the lock.)
4108 set_gc_alloc_region(purpose, alloc_region);
4110 if (par) {
4111 block = alloc_region->par_allocate(word_size);
4112 } else {
4113 block = alloc_region->allocate(word_size);
4114 }
4115 // Caller handles alloc failure.
4116 } else {
4117 // This sets other apis using the same old alloc region to NULL, also.
4118 set_gc_alloc_region(purpose, NULL);
4119 }
4120 return block; // May be NULL.
4121 }
4123 void G1CollectedHeap::par_allocate_remaining_space(HeapRegion* r) {
4124 HeapWord* block = NULL;
4125 size_t free_words;
4126 do {
4127 free_words = r->free()/HeapWordSize;
4128 // If there's too little space, no one can allocate, so we're done.
4129 if (free_words < CollectedHeap::min_fill_size()) return;
4130 // Otherwise, try to claim it.
4131 block = r->par_allocate(free_words);
4132 } while (block == NULL);
4133 fill_with_object(block, free_words);
4134 }
4136 #ifndef PRODUCT
4137 bool GCLabBitMapClosure::do_bit(size_t offset) {
4138 HeapWord* addr = _bitmap->offsetToHeapWord(offset);
4139 guarantee(_cm->isMarked(oop(addr)), "it should be!");
4140 return true;
4141 }
4142 #endif // PRODUCT
4144 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num)
4145 : _g1h(g1h),
4146 _refs(g1h->task_queue(queue_num)),
4147 _dcq(&g1h->dirty_card_queue_set()),
4148 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4149 _g1_rem(g1h->g1_rem_set()),
4150 _hash_seed(17), _queue_num(queue_num),
4151 _term_attempts(0),
4152 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4153 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4154 _age_table(false),
4155 _strong_roots_time(0), _term_time(0),
4156 _alloc_buffer_waste(0), _undo_waste(0)
4157 {
4158 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4159 // we "sacrifice" entry 0 to keep track of surviving bytes for
4160 // non-young regions (where the age is -1)
4161 // We also add a few elements at the beginning and at the end in
4162 // an attempt to eliminate cache contention
4163 size_t real_length = 1 + _g1h->g1_policy()->young_cset_length();
4164 size_t array_length = PADDING_ELEM_NUM +
4165 real_length +
4166 PADDING_ELEM_NUM;
4167 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4168 if (_surviving_young_words_base == NULL)
4169 vm_exit_out_of_memory(array_length * sizeof(size_t),
4170 "Not enough space for young surv histo.");
4171 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4172 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
4174 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4175 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4177 _start = os::elapsedTime();
4178 }
4180 void
4181 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4182 {
4183 st->print_raw_cr("GC Termination Stats");
4184 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4185 " ------waste (KiB)------");
4186 st->print_raw_cr("thr ms ms % ms % attempts"
4187 " total alloc undo");
4188 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4189 " ------- ------- -------");
4190 }
4192 void
4193 G1ParScanThreadState::print_termination_stats(int i,
4194 outputStream* const st) const
4195 {
4196 const double elapsed_ms = elapsed_time() * 1000.0;
4197 const double s_roots_ms = strong_roots_time() * 1000.0;
4198 const double term_ms = term_time() * 1000.0;
4199 st->print_cr("%3d %9.2f %9.2f %6.2f "
4200 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4201 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4202 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4203 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4204 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4205 alloc_buffer_waste() * HeapWordSize / K,
4206 undo_waste() * HeapWordSize / K);
4207 }
4209 #ifdef ASSERT
4210 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4211 assert(ref != NULL, "invariant");
4212 assert(UseCompressedOops, "sanity");
4213 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4214 oop p = oopDesc::load_decode_heap_oop(ref);
4215 assert(_g1h->is_in_g1_reserved(p),
4216 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4217 return true;
4218 }
4220 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4221 assert(ref != NULL, "invariant");
4222 if (has_partial_array_mask(ref)) {
4223 // Must be in the collection set--it's already been copied.
4224 oop p = clear_partial_array_mask(ref);
4225 assert(_g1h->obj_in_cs(p),
4226 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4227 } else {
4228 oop p = oopDesc::load_decode_heap_oop(ref);
4229 assert(_g1h->is_in_g1_reserved(p),
4230 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4231 }
4232 return true;
4233 }
4235 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4236 if (ref.is_narrow()) {
4237 return verify_ref((narrowOop*) ref);
4238 } else {
4239 return verify_ref((oop*) ref);
4240 }
4241 }
4242 #endif // ASSERT
4244 void G1ParScanThreadState::trim_queue() {
4245 StarTask ref;
4246 do {
4247 // Drain the overflow stack first, so other threads can steal.
4248 while (refs()->pop_overflow(ref)) {
4249 deal_with_reference(ref);
4250 }
4251 while (refs()->pop_local(ref)) {
4252 deal_with_reference(ref);
4253 }
4254 } while (!refs()->is_empty());
4255 }
4257 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
4258 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4259 _par_scan_state(par_scan_state) { }
4261 template <class T> void G1ParCopyHelper::mark_forwardee(T* p) {
4262 // This is called _after_ do_oop_work has been called, hence after
4263 // the object has been relocated to its new location and *p points
4264 // to its new location.
4266 T heap_oop = oopDesc::load_heap_oop(p);
4267 if (!oopDesc::is_null(heap_oop)) {
4268 oop obj = oopDesc::decode_heap_oop(heap_oop);
4269 assert((_g1->evacuation_failed()) || (!_g1->obj_in_cs(obj)),
4270 "shouldn't still be in the CSet if evacuation didn't fail.");
4271 HeapWord* addr = (HeapWord*)obj;
4272 if (_g1->is_in_g1_reserved(addr))
4273 _cm->grayRoot(oop(addr));
4274 }
4275 }
4277 oop G1ParCopyHelper::copy_to_survivor_space(oop old) {
4278 size_t word_sz = old->size();
4279 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4280 // +1 to make the -1 indexes valid...
4281 int young_index = from_region->young_index_in_cset()+1;
4282 assert( (from_region->is_young() && young_index > 0) ||
4283 (!from_region->is_young() && young_index == 0), "invariant" );
4284 G1CollectorPolicy* g1p = _g1->g1_policy();
4285 markOop m = old->mark();
4286 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4287 : m->age();
4288 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4289 word_sz);
4290 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4291 oop obj = oop(obj_ptr);
4293 if (obj_ptr == NULL) {
4294 // This will either forward-to-self, or detect that someone else has
4295 // installed a forwarding pointer.
4296 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4297 return _g1->handle_evacuation_failure_par(cl, old);
4298 }
4300 // We're going to allocate linearly, so might as well prefetch ahead.
4301 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4303 oop forward_ptr = old->forward_to_atomic(obj);
4304 if (forward_ptr == NULL) {
4305 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4306 if (g1p->track_object_age(alloc_purpose)) {
4307 // We could simply do obj->incr_age(). However, this causes a
4308 // performance issue. obj->incr_age() will first check whether
4309 // the object has a displaced mark by checking its mark word;
4310 // getting the mark word from the new location of the object
4311 // stalls. So, given that we already have the mark word and we
4312 // are about to install it anyway, it's better to increase the
4313 // age on the mark word, when the object does not have a
4314 // displaced mark word. We're not expecting many objects to have
4315 // a displaced marked word, so that case is not optimized
4316 // further (it could be...) and we simply call obj->incr_age().
4318 if (m->has_displaced_mark_helper()) {
4319 // in this case, we have to install the mark word first,
4320 // otherwise obj looks to be forwarded (the old mark word,
4321 // which contains the forward pointer, was copied)
4322 obj->set_mark(m);
4323 obj->incr_age();
4324 } else {
4325 m = m->incr_age();
4326 obj->set_mark(m);
4327 }
4328 _par_scan_state->age_table()->add(obj, word_sz);
4329 } else {
4330 obj->set_mark(m);
4331 }
4333 // preserve "next" mark bit
4334 if (_g1->mark_in_progress() && !_g1->is_obj_ill(old)) {
4335 if (!use_local_bitmaps ||
4336 !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) {
4337 // if we couldn't mark it on the local bitmap (this happens when
4338 // the object was not allocated in the GCLab), we have to bite
4339 // the bullet and do the standard parallel mark
4340 _cm->markAndGrayObjectIfNecessary(obj);
4341 }
4342 #if 1
4343 if (_g1->isMarkedNext(old)) {
4344 _cm->nextMarkBitMap()->parClear((HeapWord*)old);
4345 }
4346 #endif
4347 }
4349 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4350 surv_young_words[young_index] += word_sz;
4352 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4353 arrayOop(old)->set_length(0);
4354 oop* old_p = set_partial_array_mask(old);
4355 _par_scan_state->push_on_queue(old_p);
4356 } else {
4357 // No point in using the slower heap_region_containing() method,
4358 // given that we know obj is in the heap.
4359 _scanner->set_region(_g1->heap_region_containing_raw(obj));
4360 obj->oop_iterate_backwards(_scanner);
4361 }
4362 } else {
4363 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4364 obj = forward_ptr;
4365 }
4366 return obj;
4367 }
4369 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_forwardee>
4370 template <class T>
4371 void G1ParCopyClosure <do_gen_barrier, barrier, do_mark_forwardee>
4372 ::do_oop_work(T* p) {
4373 oop obj = oopDesc::load_decode_heap_oop(p);
4374 assert(barrier != G1BarrierRS || obj != NULL,
4375 "Precondition: G1BarrierRS implies obj is nonNull");
4377 // here the null check is implicit in the cset_fast_test() test
4378 if (_g1->in_cset_fast_test(obj)) {
4379 #if G1_REM_SET_LOGGING
4380 gclog_or_tty->print_cr("Loc "PTR_FORMAT" contains pointer "PTR_FORMAT" "
4381 "into CS.", p, (void*) obj);
4382 #endif
4383 if (obj->is_forwarded()) {
4384 oopDesc::encode_store_heap_oop(p, obj->forwardee());
4385 } else {
4386 oop copy_oop = copy_to_survivor_space(obj);
4387 oopDesc::encode_store_heap_oop(p, copy_oop);
4388 }
4389 // When scanning the RS, we only care about objs in CS.
4390 if (barrier == G1BarrierRS) {
4391 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4392 }
4393 }
4395 if (barrier == G1BarrierEvac && obj != NULL) {
4396 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4397 }
4399 if (do_gen_barrier && obj != NULL) {
4400 par_do_barrier(p);
4401 }
4402 }
4404 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4405 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4407 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4408 assert(has_partial_array_mask(p), "invariant");
4409 oop old = clear_partial_array_mask(p);
4410 assert(old->is_objArray(), "must be obj array");
4411 assert(old->is_forwarded(), "must be forwarded");
4412 assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
4414 objArrayOop obj = objArrayOop(old->forwardee());
4415 assert((void*)old != (void*)old->forwardee(), "self forwarding here?");
4416 // Process ParGCArrayScanChunk elements now
4417 // and push the remainder back onto queue
4418 int start = arrayOop(old)->length();
4419 int end = obj->length();
4420 int remainder = end - start;
4421 assert(start <= end, "just checking");
4422 if (remainder > 2 * ParGCArrayScanChunk) {
4423 // Test above combines last partial chunk with a full chunk
4424 end = start + ParGCArrayScanChunk;
4425 arrayOop(old)->set_length(end);
4426 // Push remainder.
4427 oop* old_p = set_partial_array_mask(old);
4428 assert(arrayOop(old)->length() < obj->length(), "Empty push?");
4429 _par_scan_state->push_on_queue(old_p);
4430 } else {
4431 // Restore length so that the heap remains parsable in
4432 // case of evacuation failure.
4433 arrayOop(old)->set_length(end);
4434 }
4435 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4436 // process our set of indices (include header in first chunk)
4437 obj->oop_iterate_range(&_scanner, start, end);
4438 }
4440 class G1ParEvacuateFollowersClosure : public VoidClosure {
4441 protected:
4442 G1CollectedHeap* _g1h;
4443 G1ParScanThreadState* _par_scan_state;
4444 RefToScanQueueSet* _queues;
4445 ParallelTaskTerminator* _terminator;
4447 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4448 RefToScanQueueSet* queues() { return _queues; }
4449 ParallelTaskTerminator* terminator() { return _terminator; }
4451 public:
4452 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4453 G1ParScanThreadState* par_scan_state,
4454 RefToScanQueueSet* queues,
4455 ParallelTaskTerminator* terminator)
4456 : _g1h(g1h), _par_scan_state(par_scan_state),
4457 _queues(queues), _terminator(terminator) {}
4459 void do_void();
4461 private:
4462 inline bool offer_termination();
4463 };
4465 bool G1ParEvacuateFollowersClosure::offer_termination() {
4466 G1ParScanThreadState* const pss = par_scan_state();
4467 pss->start_term_time();
4468 const bool res = terminator()->offer_termination();
4469 pss->end_term_time();
4470 return res;
4471 }
4473 void G1ParEvacuateFollowersClosure::do_void() {
4474 StarTask stolen_task;
4475 G1ParScanThreadState* const pss = par_scan_state();
4476 pss->trim_queue();
4478 do {
4479 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4480 assert(pss->verify_task(stolen_task), "sanity");
4481 if (stolen_task.is_narrow()) {
4482 pss->deal_with_reference((narrowOop*) stolen_task);
4483 } else {
4484 pss->deal_with_reference((oop*) stolen_task);
4485 }
4487 // We've just processed a reference and we might have made
4488 // available new entries on the queues. So we have to make sure
4489 // we drain the queues as necessary.
4490 pss->trim_queue();
4491 }
4492 } while (!offer_termination());
4494 pss->retire_alloc_buffers();
4495 }
4497 class G1ParTask : public AbstractGangTask {
4498 protected:
4499 G1CollectedHeap* _g1h;
4500 RefToScanQueueSet *_queues;
4501 ParallelTaskTerminator _terminator;
4502 int _n_workers;
4504 Mutex _stats_lock;
4505 Mutex* stats_lock() { return &_stats_lock; }
4507 size_t getNCards() {
4508 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4509 / G1BlockOffsetSharedArray::N_bytes;
4510 }
4512 public:
4513 G1ParTask(G1CollectedHeap* g1h, int workers, RefToScanQueueSet *task_queues)
4514 : AbstractGangTask("G1 collection"),
4515 _g1h(g1h),
4516 _queues(task_queues),
4517 _terminator(workers, _queues),
4518 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true),
4519 _n_workers(workers)
4520 {}
4522 RefToScanQueueSet* queues() { return _queues; }
4524 RefToScanQueue *work_queue(int i) {
4525 return queues()->queue(i);
4526 }
4528 void work(int i) {
4529 if (i >= _n_workers) return; // no work needed this round
4531 double start_time_ms = os::elapsedTime() * 1000.0;
4532 _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms);
4534 ResourceMark rm;
4535 HandleMark hm;
4537 G1ParScanThreadState pss(_g1h, i);
4538 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss);
4539 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss);
4540 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss);
4542 pss.set_evac_closure(&scan_evac_cl);
4543 pss.set_evac_failure_closure(&evac_failure_cl);
4544 pss.set_partial_scan_closure(&partial_scan_cl);
4546 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss);
4547 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss);
4548 G1ParScanHeapRSClosure only_scan_heap_rs_cl(_g1h, &pss);
4549 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4551 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss);
4552 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss);
4553 G1ParScanAndMarkHeapRSClosure scan_mark_heap_rs_cl(_g1h, &pss);
4555 OopsInHeapRegionClosure *scan_root_cl;
4556 OopsInHeapRegionClosure *scan_perm_cl;
4558 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4559 scan_root_cl = &scan_mark_root_cl;
4560 scan_perm_cl = &scan_mark_perm_cl;
4561 } else {
4562 scan_root_cl = &only_scan_root_cl;
4563 scan_perm_cl = &only_scan_perm_cl;
4564 }
4566 pss.start_strong_roots();
4567 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4568 SharedHeap::SO_AllClasses,
4569 scan_root_cl,
4570 &push_heap_rs_cl,
4571 scan_perm_cl,
4572 i);
4573 pss.end_strong_roots();
4574 {
4575 double start = os::elapsedTime();
4576 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4577 evac.do_void();
4578 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4579 double term_ms = pss.term_time()*1000.0;
4580 _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms);
4581 _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts());
4582 }
4583 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4584 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4586 // Clean up any par-expanded rem sets.
4587 HeapRegionRemSet::par_cleanup();
4589 if (ParallelGCVerbose) {
4590 MutexLocker x(stats_lock());
4591 pss.print_termination_stats(i);
4592 }
4594 assert(pss.refs()->is_empty(), "should be empty");
4595 double end_time_ms = os::elapsedTime() * 1000.0;
4596 _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
4597 }
4598 };
4600 // *** Common G1 Evacuation Stuff
4602 // This method is run in a GC worker.
4604 void
4605 G1CollectedHeap::
4606 g1_process_strong_roots(bool collecting_perm_gen,
4607 SharedHeap::ScanningOption so,
4608 OopClosure* scan_non_heap_roots,
4609 OopsInHeapRegionClosure* scan_rs,
4610 OopsInGenClosure* scan_perm,
4611 int worker_i) {
4612 // First scan the strong roots, including the perm gen.
4613 double ext_roots_start = os::elapsedTime();
4614 double closure_app_time_sec = 0.0;
4616 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4617 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4618 buf_scan_perm.set_generation(perm_gen());
4620 // Walk the code cache w/o buffering, because StarTask cannot handle
4621 // unaligned oop locations.
4622 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
4624 process_strong_roots(false, // no scoping; this is parallel code
4625 collecting_perm_gen, so,
4626 &buf_scan_non_heap_roots,
4627 &eager_scan_code_roots,
4628 &buf_scan_perm);
4630 // Finish up any enqueued closure apps.
4631 buf_scan_non_heap_roots.done();
4632 buf_scan_perm.done();
4633 double ext_roots_end = os::elapsedTime();
4634 g1_policy()->reset_obj_copy_time(worker_i);
4635 double obj_copy_time_sec =
4636 buf_scan_non_heap_roots.closure_app_seconds() +
4637 buf_scan_perm.closure_app_seconds();
4638 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4639 double ext_root_time_ms =
4640 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4641 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4643 // Scan strong roots in mark stack.
4644 if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) {
4645 concurrent_mark()->oops_do(scan_non_heap_roots);
4646 }
4647 double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4648 g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms);
4650 // XXX What should this be doing in the parallel case?
4651 g1_policy()->record_collection_pause_end_CH_strong_roots();
4652 // Now scan the complement of the collection set.
4653 if (scan_rs != NULL) {
4654 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4655 }
4656 // Finish with the ref_processor roots.
4657 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4658 // We need to treat the discovered reference lists as roots and
4659 // keep entries (which are added by the marking threads) on them
4660 // live until they can be processed at the end of marking.
4661 ref_processor()->weak_oops_do(scan_non_heap_roots);
4662 ref_processor()->oops_do(scan_non_heap_roots);
4663 }
4664 g1_policy()->record_collection_pause_end_G1_strong_roots();
4665 _process_strong_tasks->all_tasks_completed();
4666 }
4668 void
4669 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4670 OopClosure* non_root_closure) {
4671 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4672 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4673 }
4676 class SaveMarksClosure: public HeapRegionClosure {
4677 public:
4678 bool doHeapRegion(HeapRegion* r) {
4679 r->save_marks();
4680 return false;
4681 }
4682 };
4684 void G1CollectedHeap::save_marks() {
4685 if (!CollectedHeap::use_parallel_gc_threads()) {
4686 SaveMarksClosure sm;
4687 heap_region_iterate(&sm);
4688 }
4689 // We do this even in the parallel case
4690 perm_gen()->save_marks();
4691 }
4693 void G1CollectedHeap::evacuate_collection_set() {
4694 set_evacuation_failed(false);
4696 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4697 concurrent_g1_refine()->set_use_cache(false);
4698 concurrent_g1_refine()->clear_hot_cache_claimed_index();
4700 int n_workers = (ParallelGCThreads > 0 ? workers()->total_workers() : 1);
4701 set_par_threads(n_workers);
4702 G1ParTask g1_par_task(this, n_workers, _task_queues);
4704 init_for_evac_failure(NULL);
4706 rem_set()->prepare_for_younger_refs_iterate(true);
4708 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4709 double start_par = os::elapsedTime();
4710 if (G1CollectedHeap::use_parallel_gc_threads()) {
4711 // The individual threads will set their evac-failure closures.
4712 StrongRootsScope srs(this);
4713 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
4714 workers()->run_task(&g1_par_task);
4715 } else {
4716 StrongRootsScope srs(this);
4717 g1_par_task.work(0);
4718 }
4720 double par_time = (os::elapsedTime() - start_par) * 1000.0;
4721 g1_policy()->record_par_time(par_time);
4722 set_par_threads(0);
4723 // Is this the right thing to do here? We don't save marks
4724 // on individual heap regions when we allocate from
4725 // them in parallel, so this seems like the correct place for this.
4726 retire_all_alloc_regions();
4728 // Weak root processing.
4729 // Note: when JSR 292 is enabled and code blobs can contain
4730 // non-perm oops then we will need to process the code blobs
4731 // here too.
4732 {
4733 G1IsAliveClosure is_alive(this);
4734 G1KeepAliveClosure keep_alive(this);
4735 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4736 }
4737 release_gc_alloc_regions(false /* totally */);
4738 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4740 concurrent_g1_refine()->clear_hot_cache();
4741 concurrent_g1_refine()->set_use_cache(true);
4743 finalize_for_evac_failure();
4745 // Must do this before removing self-forwarding pointers, which clears
4746 // the per-region evac-failure flags.
4747 concurrent_mark()->complete_marking_in_collection_set();
4749 if (evacuation_failed()) {
4750 remove_self_forwarding_pointers();
4751 if (PrintGCDetails) {
4752 gclog_or_tty->print(" (to-space overflow)");
4753 } else if (PrintGC) {
4754 gclog_or_tty->print("--");
4755 }
4756 }
4758 if (G1DeferredRSUpdate) {
4759 RedirtyLoggedCardTableEntryFastClosure redirty;
4760 dirty_card_queue_set().set_closure(&redirty);
4761 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
4763 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4764 dcq.merge_bufferlists(&dirty_card_queue_set());
4765 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4766 }
4767 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
4768 }
4770 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
4771 size_t* pre_used,
4772 FreeRegionList* free_list,
4773 HumongousRegionSet* humongous_proxy_set,
4774 HRRSCleanupTask* hrrs_cleanup_task,
4775 bool par) {
4776 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
4777 if (hr->isHumongous()) {
4778 assert(hr->startsHumongous(), "we should only see starts humongous");
4779 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
4780 } else {
4781 free_region(hr, pre_used, free_list, par);
4782 }
4783 } else {
4784 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
4785 }
4786 }
4788 void G1CollectedHeap::free_region(HeapRegion* hr,
4789 size_t* pre_used,
4790 FreeRegionList* free_list,
4791 bool par) {
4792 assert(!hr->isHumongous(), "this is only for non-humongous regions");
4793 assert(!hr->is_empty(), "the region should not be empty");
4794 assert(free_list != NULL, "pre-condition");
4796 *pre_used += hr->used();
4797 hr->hr_clear(par, true /* clear_space */);
4798 free_list->add_as_head(hr);
4799 }
4801 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4802 size_t* pre_used,
4803 FreeRegionList* free_list,
4804 HumongousRegionSet* humongous_proxy_set,
4805 bool par) {
4806 assert(hr->startsHumongous(), "this is only for starts humongous regions");
4807 assert(free_list != NULL, "pre-condition");
4808 assert(humongous_proxy_set != NULL, "pre-condition");
4810 size_t hr_used = hr->used();
4811 size_t hr_capacity = hr->capacity();
4812 size_t hr_pre_used = 0;
4813 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
4814 hr->set_notHumongous();
4815 free_region(hr, &hr_pre_used, free_list, par);
4817 int i = hr->hrs_index() + 1;
4818 size_t num = 1;
4819 while ((size_t) i < n_regions()) {
4820 HeapRegion* curr_hr = _hrs->at(i);
4821 if (!curr_hr->continuesHumongous()) {
4822 break;
4823 }
4824 curr_hr->set_notHumongous();
4825 free_region(curr_hr, &hr_pre_used, free_list, par);
4826 num += 1;
4827 i += 1;
4828 }
4829 assert(hr_pre_used == hr_used,
4830 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
4831 "should be the same", hr_pre_used, hr_used));
4832 *pre_used += hr_pre_used;
4833 }
4835 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
4836 FreeRegionList* free_list,
4837 HumongousRegionSet* humongous_proxy_set,
4838 bool par) {
4839 if (pre_used > 0) {
4840 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
4841 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
4842 assert(_summary_bytes_used >= pre_used,
4843 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
4844 "should be >= pre_used: "SIZE_FORMAT,
4845 _summary_bytes_used, pre_used));
4846 _summary_bytes_used -= pre_used;
4847 }
4848 if (free_list != NULL && !free_list->is_empty()) {
4849 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4850 _free_list.add_as_head(free_list);
4851 }
4852 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
4853 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4854 _humongous_set.update_from_proxy(humongous_proxy_set);
4855 }
4856 }
4858 void G1CollectedHeap::dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list) {
4859 while (list != NULL) {
4860 guarantee( list->is_young(), "invariant" );
4862 HeapWord* bottom = list->bottom();
4863 HeapWord* end = list->end();
4864 MemRegion mr(bottom, end);
4865 ct_bs->dirty(mr);
4867 list = list->get_next_young_region();
4868 }
4869 }
4872 class G1ParCleanupCTTask : public AbstractGangTask {
4873 CardTableModRefBS* _ct_bs;
4874 G1CollectedHeap* _g1h;
4875 HeapRegion* volatile _su_head;
4876 public:
4877 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
4878 G1CollectedHeap* g1h,
4879 HeapRegion* survivor_list) :
4880 AbstractGangTask("G1 Par Cleanup CT Task"),
4881 _ct_bs(ct_bs),
4882 _g1h(g1h),
4883 _su_head(survivor_list)
4884 { }
4886 void work(int i) {
4887 HeapRegion* r;
4888 while (r = _g1h->pop_dirty_cards_region()) {
4889 clear_cards(r);
4890 }
4891 // Redirty the cards of the survivor regions.
4892 dirty_list(&this->_su_head);
4893 }
4895 void clear_cards(HeapRegion* r) {
4896 // Cards for Survivor regions will be dirtied later.
4897 if (!r->is_survivor()) {
4898 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
4899 }
4900 }
4902 void dirty_list(HeapRegion* volatile * head_ptr) {
4903 HeapRegion* head;
4904 do {
4905 // Pop region off the list.
4906 head = *head_ptr;
4907 if (head != NULL) {
4908 HeapRegion* r = (HeapRegion*)
4909 Atomic::cmpxchg_ptr(head->get_next_young_region(), head_ptr, head);
4910 if (r == head) {
4911 assert(!r->isHumongous(), "Humongous regions shouldn't be on survivor list");
4912 _ct_bs->dirty(MemRegion(r->bottom(), r->end()));
4913 }
4914 }
4915 } while (*head_ptr != NULL);
4916 }
4917 };
4920 #ifndef PRODUCT
4921 class G1VerifyCardTableCleanup: public HeapRegionClosure {
4922 CardTableModRefBS* _ct_bs;
4923 public:
4924 G1VerifyCardTableCleanup(CardTableModRefBS* ct_bs)
4925 : _ct_bs(ct_bs) { }
4926 virtual bool doHeapRegion(HeapRegion* r) {
4927 MemRegion mr(r->bottom(), r->end());
4928 if (r->is_survivor()) {
4929 _ct_bs->verify_dirty_region(mr);
4930 } else {
4931 _ct_bs->verify_clean_region(mr);
4932 }
4933 return false;
4934 }
4935 };
4937 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
4938 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
4939 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
4940 // We cannot guarantee that [bottom(),end()] is dirty. Threads
4941 // dirty allocated blocks as they allocate them. The thread that
4942 // retires each region and replaces it with a new one will do a
4943 // maximal allocation to fill in [pre_dummy_top(),end()] but will
4944 // not dirty that area (one less thing to have to do while holding
4945 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
4946 // is dirty. Also note that verify_dirty_region() requires
4947 // mr.start() and mr.end() to be card aligned and pre_dummy_top()
4948 // is not guaranteed to be.
4949 MemRegion mr(hr->bottom(),
4950 ct_bs->align_to_card_boundary(hr->pre_dummy_top()));
4951 ct_bs->verify_dirty_region(mr);
4952 }
4953 }
4955 void G1CollectedHeap::verify_dirty_young_regions() {
4956 verify_dirty_young_list(_young_list->first_region());
4957 verify_dirty_young_list(_young_list->first_survivor_region());
4958 }
4959 #endif
4961 void G1CollectedHeap::cleanUpCardTable() {
4962 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
4963 double start = os::elapsedTime();
4965 // Iterate over the dirty cards region list.
4966 G1ParCleanupCTTask cleanup_task(ct_bs, this,
4967 _young_list->first_survivor_region());
4969 if (ParallelGCThreads > 0) {
4970 set_par_threads(workers()->total_workers());
4971 workers()->run_task(&cleanup_task);
4972 set_par_threads(0);
4973 } else {
4974 while (_dirty_cards_region_list) {
4975 HeapRegion* r = _dirty_cards_region_list;
4976 cleanup_task.clear_cards(r);
4977 _dirty_cards_region_list = r->get_next_dirty_cards_region();
4978 if (_dirty_cards_region_list == r) {
4979 // The last region.
4980 _dirty_cards_region_list = NULL;
4981 }
4982 r->set_next_dirty_cards_region(NULL);
4983 }
4984 // now, redirty the cards of the survivor regions
4985 // (it seemed faster to do it this way, instead of iterating over
4986 // all regions and then clearing / dirtying as appropriate)
4987 dirtyCardsForYoungRegions(ct_bs, _young_list->first_survivor_region());
4988 }
4990 double elapsed = os::elapsedTime() - start;
4991 g1_policy()->record_clear_ct_time( elapsed * 1000.0);
4992 #ifndef PRODUCT
4993 if (G1VerifyCTCleanup || VerifyAfterGC) {
4994 G1VerifyCardTableCleanup cleanup_verifier(ct_bs);
4995 heap_region_iterate(&cleanup_verifier);
4996 }
4997 #endif
4998 }
5000 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5001 size_t pre_used = 0;
5002 FreeRegionList local_free_list("Local List for CSet Freeing");
5004 double young_time_ms = 0.0;
5005 double non_young_time_ms = 0.0;
5007 // Since the collection set is a superset of the the young list,
5008 // all we need to do to clear the young list is clear its
5009 // head and length, and unlink any young regions in the code below
5010 _young_list->clear();
5012 G1CollectorPolicy* policy = g1_policy();
5014 double start_sec = os::elapsedTime();
5015 bool non_young = true;
5017 HeapRegion* cur = cs_head;
5018 int age_bound = -1;
5019 size_t rs_lengths = 0;
5021 while (cur != NULL) {
5022 assert(!is_on_master_free_list(cur), "sanity");
5024 if (non_young) {
5025 if (cur->is_young()) {
5026 double end_sec = os::elapsedTime();
5027 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5028 non_young_time_ms += elapsed_ms;
5030 start_sec = os::elapsedTime();
5031 non_young = false;
5032 }
5033 } else {
5034 double end_sec = os::elapsedTime();
5035 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5036 young_time_ms += elapsed_ms;
5038 start_sec = os::elapsedTime();
5039 non_young = true;
5040 }
5042 rs_lengths += cur->rem_set()->occupied();
5044 HeapRegion* next = cur->next_in_collection_set();
5045 assert(cur->in_collection_set(), "bad CS");
5046 cur->set_next_in_collection_set(NULL);
5047 cur->set_in_collection_set(false);
5049 if (cur->is_young()) {
5050 int index = cur->young_index_in_cset();
5051 guarantee( index != -1, "invariant" );
5052 guarantee( (size_t)index < policy->young_cset_length(), "invariant" );
5053 size_t words_survived = _surviving_young_words[index];
5054 cur->record_surv_words_in_group(words_survived);
5056 // At this point the we have 'popped' cur from the collection set
5057 // (linked via next_in_collection_set()) but it is still in the
5058 // young list (linked via next_young_region()). Clear the
5059 // _next_young_region field.
5060 cur->set_next_young_region(NULL);
5061 } else {
5062 int index = cur->young_index_in_cset();
5063 guarantee( index == -1, "invariant" );
5064 }
5066 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5067 (!cur->is_young() && cur->young_index_in_cset() == -1),
5068 "invariant" );
5070 if (!cur->evacuation_failed()) {
5071 // And the region is empty.
5072 assert(!cur->is_empty(), "Should not have empty regions in a CS.");
5073 free_region(cur, &pre_used, &local_free_list, false /* par */);
5074 } else {
5075 cur->uninstall_surv_rate_group();
5076 if (cur->is_young())
5077 cur->set_young_index_in_cset(-1);
5078 cur->set_not_young();
5079 cur->set_evacuation_failed(false);
5080 }
5081 cur = next;
5082 }
5084 policy->record_max_rs_lengths(rs_lengths);
5085 policy->cset_regions_freed();
5087 double end_sec = os::elapsedTime();
5088 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5089 if (non_young)
5090 non_young_time_ms += elapsed_ms;
5091 else
5092 young_time_ms += elapsed_ms;
5094 update_sets_after_freeing_regions(pre_used, &local_free_list,
5095 NULL /* humongous_proxy_set */,
5096 false /* par */);
5097 policy->record_young_free_cset_time_ms(young_time_ms);
5098 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5099 }
5101 // This routine is similar to the above but does not record
5102 // any policy statistics or update free lists; we are abandoning
5103 // the current incremental collection set in preparation of a
5104 // full collection. After the full GC we will start to build up
5105 // the incremental collection set again.
5106 // This is only called when we're doing a full collection
5107 // and is immediately followed by the tearing down of the young list.
5109 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5110 HeapRegion* cur = cs_head;
5112 while (cur != NULL) {
5113 HeapRegion* next = cur->next_in_collection_set();
5114 assert(cur->in_collection_set(), "bad CS");
5115 cur->set_next_in_collection_set(NULL);
5116 cur->set_in_collection_set(false);
5117 cur->set_young_index_in_cset(-1);
5118 cur = next;
5119 }
5120 }
5122 void G1CollectedHeap::set_free_regions_coming() {
5123 if (G1ConcRegionFreeingVerbose) {
5124 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5125 "setting free regions coming");
5126 }
5128 assert(!free_regions_coming(), "pre-condition");
5129 _free_regions_coming = true;
5130 }
5132 void G1CollectedHeap::reset_free_regions_coming() {
5133 {
5134 assert(free_regions_coming(), "pre-condition");
5135 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5136 _free_regions_coming = false;
5137 SecondaryFreeList_lock->notify_all();
5138 }
5140 if (G1ConcRegionFreeingVerbose) {
5141 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5142 "reset free regions coming");
5143 }
5144 }
5146 void G1CollectedHeap::wait_while_free_regions_coming() {
5147 // Most of the time we won't have to wait, so let's do a quick test
5148 // first before we take the lock.
5149 if (!free_regions_coming()) {
5150 return;
5151 }
5153 if (G1ConcRegionFreeingVerbose) {
5154 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5155 "waiting for free regions");
5156 }
5158 {
5159 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5160 while (free_regions_coming()) {
5161 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5162 }
5163 }
5165 if (G1ConcRegionFreeingVerbose) {
5166 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5167 "done waiting for free regions");
5168 }
5169 }
5171 size_t G1CollectedHeap::n_regions() {
5172 return _hrs->length();
5173 }
5175 size_t G1CollectedHeap::max_regions() {
5176 return
5177 (size_t)align_size_up(max_capacity(), HeapRegion::GrainBytes) /
5178 HeapRegion::GrainBytes;
5179 }
5181 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5182 assert(heap_lock_held_for_gc(),
5183 "the heap lock should already be held by or for this thread");
5184 _young_list->push_region(hr);
5185 g1_policy()->set_region_short_lived(hr);
5186 }
5188 class NoYoungRegionsClosure: public HeapRegionClosure {
5189 private:
5190 bool _success;
5191 public:
5192 NoYoungRegionsClosure() : _success(true) { }
5193 bool doHeapRegion(HeapRegion* r) {
5194 if (r->is_young()) {
5195 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5196 r->bottom(), r->end());
5197 _success = false;
5198 }
5199 return false;
5200 }
5201 bool success() { return _success; }
5202 };
5204 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5205 bool ret = _young_list->check_list_empty(check_sample);
5207 if (check_heap) {
5208 NoYoungRegionsClosure closure;
5209 heap_region_iterate(&closure);
5210 ret = ret && closure.success();
5211 }
5213 return ret;
5214 }
5216 void G1CollectedHeap::empty_young_list() {
5217 assert(heap_lock_held_for_gc(),
5218 "the heap lock should already be held by or for this thread");
5219 assert(g1_policy()->in_young_gc_mode(), "should be in young GC mode");
5221 _young_list->empty_list();
5222 }
5224 bool G1CollectedHeap::all_alloc_regions_no_allocs_since_save_marks() {
5225 bool no_allocs = true;
5226 for (int ap = 0; ap < GCAllocPurposeCount && no_allocs; ++ap) {
5227 HeapRegion* r = _gc_alloc_regions[ap];
5228 no_allocs = r == NULL || r->saved_mark_at_top();
5229 }
5230 return no_allocs;
5231 }
5233 void G1CollectedHeap::retire_all_alloc_regions() {
5234 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
5235 HeapRegion* r = _gc_alloc_regions[ap];
5236 if (r != NULL) {
5237 // Check for aliases.
5238 bool has_processed_alias = false;
5239 for (int i = 0; i < ap; ++i) {
5240 if (_gc_alloc_regions[i] == r) {
5241 has_processed_alias = true;
5242 break;
5243 }
5244 }
5245 if (!has_processed_alias) {
5246 retire_alloc_region(r, false /* par */);
5247 }
5248 }
5249 }
5250 }
5252 // Done at the start of full GC.
5253 void G1CollectedHeap::tear_down_region_lists() {
5254 _free_list.remove_all();
5255 }
5257 class RegionResetter: public HeapRegionClosure {
5258 G1CollectedHeap* _g1h;
5259 FreeRegionList _local_free_list;
5261 public:
5262 RegionResetter() : _g1h(G1CollectedHeap::heap()),
5263 _local_free_list("Local Free List for RegionResetter") { }
5265 bool doHeapRegion(HeapRegion* r) {
5266 if (r->continuesHumongous()) return false;
5267 if (r->top() > r->bottom()) {
5268 if (r->top() < r->end()) {
5269 Copy::fill_to_words(r->top(),
5270 pointer_delta(r->end(), r->top()));
5271 }
5272 } else {
5273 assert(r->is_empty(), "tautology");
5274 _local_free_list.add_as_tail(r);
5275 }
5276 return false;
5277 }
5279 void update_free_lists() {
5280 _g1h->update_sets_after_freeing_regions(0, &_local_free_list, NULL,
5281 false /* par */);
5282 }
5283 };
5285 // Done at the end of full GC.
5286 void G1CollectedHeap::rebuild_region_lists() {
5287 // This needs to go at the end of the full GC.
5288 RegionResetter rs;
5289 heap_region_iterate(&rs);
5290 rs.update_free_lists();
5291 }
5293 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5294 _refine_cte_cl->set_concurrent(concurrent);
5295 }
5297 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5298 HeapRegion* hr = heap_region_containing(p);
5299 if (hr == NULL) {
5300 return is_in_permanent(p);
5301 } else {
5302 return hr->is_in(p);
5303 }
5304 }
5306 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5307 bool force) {
5308 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5309 assert(!force || g1_policy()->can_expand_young_list(),
5310 "if force is true we should be able to expand the young list");
5311 if (force || !g1_policy()->is_young_list_full()) {
5312 HeapRegion* new_alloc_region = new_region(word_size,
5313 false /* do_expand */);
5314 if (new_alloc_region != NULL) {
5315 g1_policy()->update_region_num(true /* next_is_young */);
5316 set_region_short_lived_locked(new_alloc_region);
5317 return new_alloc_region;
5318 }
5319 }
5320 return NULL;
5321 }
5323 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5324 size_t allocated_bytes) {
5325 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5326 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
5328 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
5329 _summary_bytes_used += allocated_bytes;
5330 }
5332 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
5333 bool force) {
5334 return _g1h->new_mutator_alloc_region(word_size, force);
5335 }
5337 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
5338 size_t allocated_bytes) {
5339 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
5340 }
5342 // Heap region set verification
5344 class VerifyRegionListsClosure : public HeapRegionClosure {
5345 private:
5346 HumongousRegionSet* _humongous_set;
5347 FreeRegionList* _free_list;
5348 size_t _region_count;
5350 public:
5351 VerifyRegionListsClosure(HumongousRegionSet* humongous_set,
5352 FreeRegionList* free_list) :
5353 _humongous_set(humongous_set), _free_list(free_list),
5354 _region_count(0) { }
5356 size_t region_count() { return _region_count; }
5358 bool doHeapRegion(HeapRegion* hr) {
5359 _region_count += 1;
5361 if (hr->continuesHumongous()) {
5362 return false;
5363 }
5365 if (hr->is_young()) {
5366 // TODO
5367 } else if (hr->startsHumongous()) {
5368 _humongous_set->verify_next_region(hr);
5369 } else if (hr->is_empty()) {
5370 _free_list->verify_next_region(hr);
5371 }
5372 return false;
5373 }
5374 };
5376 void G1CollectedHeap::verify_region_sets() {
5377 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5379 // First, check the explicit lists.
5380 _free_list.verify();
5381 {
5382 // Given that a concurrent operation might be adding regions to
5383 // the secondary free list we have to take the lock before
5384 // verifying it.
5385 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5386 _secondary_free_list.verify();
5387 }
5388 _humongous_set.verify();
5390 // If a concurrent region freeing operation is in progress it will
5391 // be difficult to correctly attributed any free regions we come
5392 // across to the correct free list given that they might belong to
5393 // one of several (free_list, secondary_free_list, any local lists,
5394 // etc.). So, if that's the case we will skip the rest of the
5395 // verification operation. Alternatively, waiting for the concurrent
5396 // operation to complete will have a non-trivial effect on the GC's
5397 // operation (no concurrent operation will last longer than the
5398 // interval between two calls to verification) and it might hide
5399 // any issues that we would like to catch during testing.
5400 if (free_regions_coming()) {
5401 return;
5402 }
5404 // Make sure we append the secondary_free_list on the free_list so
5405 // that all free regions we will come across can be safely
5406 // attributed to the free_list.
5407 append_secondary_free_list_if_not_empty_with_lock();
5409 // Finally, make sure that the region accounting in the lists is
5410 // consistent with what we see in the heap.
5411 _humongous_set.verify_start();
5412 _free_list.verify_start();
5414 VerifyRegionListsClosure cl(&_humongous_set, &_free_list);
5415 heap_region_iterate(&cl);
5417 _humongous_set.verify_end();
5418 _free_list.verify_end();
5419 }